JP4994203B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus such as a digital copying apparatus, a printer, and a FAX, and is obtained in particular by a scanner (such as a unit mounted on a color copying apparatus) attached to the image processing apparatus in advance. The present invention relates to an image processing apparatus having a connected output function for outputting original document data by another printer (which is also a unit constituting a color copying apparatus).

  Conventionally, due to variations in the spectral sensitivity of the CCD of the scanner, variations in the spectral sensitivity of the infrared cut filter for removing infrared light components, deterioration over time of the scanner optical system, etc. Even if the same color original is read, the output image signal is different for each machine, and as a result, the color output on the display and the printed color may be different.

  Patent Document 1 discloses setting image processing parameters for the purpose of reducing scanner machine differences by using a reference chart on which a plurality of color images having different gradation levels are formed.

JP 2006-238408 A

  However, in a color image forming apparatus such as a color copying machine, the calculation result of the optimum parameter described above is obtained due to the recalculation time for generating the image processing parameter from the scanner machine difference information and the memory size for storing the intermediate result. There is a problem that conditions and functions that can be applied are limited.

  The present invention has been made in view of the above. By minimizing the number of calculations, the time required for the calculation can be minimized, and the setting condition of the user to adapt the correction of the scanner difference can be expanded. As a result, an object of the present invention is to provide an image processing apparatus capable of obtaining color reproducibility preferable for read image data and printed matter.

In order to solve the above-described problems and achieve the object, an image processing apparatus according to a first aspect of the present invention is a method for converting the gradation of an input image signal from an image reading unit that optically scans and reads a document image. Converting an image signal after gradation conversion by a gradation conversion table of one image signal conversion means, a plurality of hues formed in a color space with boundaries provided parallel to the lightness axis as boundaries Stores reference data corresponding to patches in a reference chart comprising a plurality of different achromatic color patches and a plurality of different chromatic color patches, and a color correction means having a correction means for correcting the signal color according to the area. The reference data storage means, the reference chart is read by the image reading means, and the color correction means is set based on the reference data and the read value of the reference chart. Correction parameter generating means for generating image processing parameters, intermediate result holding means for calculating and holding intermediate calculation results for obtaining the image processing parameters step by step for each predetermined operation, and replaying the intermediate calculation results. Determination information storage means for storing recalculation determination information for determining whether or not to calculate, and whether to recalculate the intermediate calculation result based on the recalculation determination information, and recalculation Recalculating means for recalculating the intermediate calculation result, and the correction parameter generating means is based on the intermediate calculation result that has been recalculated or the intermediate calculation result that has not been recalculated. The image processing parameter is generated.

  According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the intermediate result holding means is at least at power-on, initialization, reference chart reading, document reading, and image data processing. During any one or more operations, the intermediate calculation result is calculated stepwise.

  According to a third aspect of the present invention, in the image processing apparatus according to the first or second aspect, the image processing parameter corrects the gradation conversion table of the first image signal conversion unit or the image signal. It is set to one of the correction means.

  According to a fourth aspect of the present invention, in the image processing apparatus according to the third aspect, the color correction unit is a masking process that uses linear masking coefficients corresponding to a plurality of hues, and the linear masking coefficients are calculated. Means for holding an intermediate result of each stage for calculation is determined, and execution / non-execution of recalculation of the coefficient of the intermediate calculation result is determined for each hue.

  According to a fifth aspect of the present invention, in the image processing apparatus according to any one of the first to fourth aspects, reading of the reference chart is prohibited until a predetermined time has elapsed after the power is turned on.

  According to a sixth aspect of the present invention, in the image processing apparatus according to the fourth or fifth aspect, the intermediate calculation result for calculating the linear masking coefficient is provided for each document type, and whether the calculation is performed for each document type. Can be selected.

  According to a seventh aspect of the present invention, in the image processing device according to any one of the first to sixth aspects, the held intermediate calculation result is increased or decreased depending on the usable volatile memory amount.

  According to an eighth aspect of the present invention, in the image processing apparatus according to any one of the first to seventh aspects, when the image reading unit includes a plurality of the image reading units, the intermediate calculation result is obtained for each image reading unit. Have.

  According to a ninth aspect of the present invention, in the image processing apparatus according to any one of the first to eighth aspects, by comparing the held intermediate calculation result with the newly corrected intermediate calculation result, Whether to recalculate the intermediate calculation result or the image processing parameter.

  According to a tenth aspect of the present invention, in the image processing apparatus according to any one of the first to ninth aspects, means for storing a first correction amount used for obtaining the image processing parameter, and the reference value Means for calculating a difference between the second correction amount obtained by newly reading the chart, and means for storing a threshold for the difference between the first correction amount and the second correction amount. Then, based on the result of comparing the difference between the first correction amount and the second correction amount with a threshold value, it is determined to recalculate the intermediate calculation result of the image processing parameter.

  According to the first aspect of the present invention, the intermediate calculation result for obtaining the image processing parameter is calculated stepwise for each predetermined operation when the optimum image processing parameter corrected for the scanner difference is applied. Recalculation decision information for deciding whether or not to recalculate intermediate calculation results is stored, recalculation of intermediate calculation results is determined based on the recalculation decision information, and image processing parameters are generated to calculate Since the time required for calculation can be minimized by minimizing the number of times, it is possible to widen the user's setting conditions for applying correction for scanner differences, and as a result, to read image data and printed matter. There is an effect that preferable color reproducibility can be obtained.

  Moreover, according to the invention concerning Claim 2, there exists an effect that calculation time can be divided | segmented.

  Further, according to the invention of claim 3, it is possible to correct the gray balance deviation of the scanner, to correct the machine difference of gradation, to correct the machine difference of the output achromatic color, There is an effect that it is possible to correct the machine signal difference between the saturation, brightness, and hue of the chromatic color and to correct and output the image signal obtained by reading.

  According to the invention of claim 4, difference information for determining whether to recalculate execution / non-execution of recalculation of the intermediate result of each stage for each hue of each linear masking coefficient in the 12 hue region By switching appropriately based on the above, the calculation time can be shortened.

  According to the fifth aspect of the present invention, the color temperature and output of the read value of the scanner are stabilized and an appropriate correction value can be obtained by reading the reference chart after a predetermined time has elapsed after turning on the power. , Has the effect.

  According to the invention of claim 6, for each hue of each masking coefficient in the 12 hue region, execution / non-execution of the recalculation of the intermediate calculation result at each stage is the difference information for determining the recalculation. By switching appropriately based on the above, the calculation time can be shortened.

  According to the invention of claim 7, in an apparatus having a sufficient amount of volatile memory (RAM), image processing parameters corresponding to conditions set by the operation unit are maintained by holding various intermediate calculation results. This calculation can be completed in a shorter time than when the memory is small. On the other hand, if the amount of installed memory is small due to cost reduction, the amount of holding intermediate results can be reduced, the amount of calculation can be reduced, or a value can be selected from a fixed table. As a result, it is possible to perform appropriate processing depending on the amount of memory.

  Further, according to the invention according to claim 8, by storing the intermediate calculation results for each of the image reading means, the calculation time can be reduced even when a plurality of image reading means are provided. Play.

  Moreover, according to the invention concerning Claim 9, there exists an effect that it becomes possible to reduce unnecessary calculation.

  According to the invention of claim 10, the previous correction value and the newly obtained correction value are compared, and if the change is small, even if recalculation is performed, the image processing parameter and Since the image processing result does not change, when the amount of change is smaller than a predetermined threshold, the intermediate result is not recalculated, thereby reducing the time for recalculating the image processing parameter while maintaining the image quality. There is an effect that it is possible.

  Exemplary embodiments of an image processing apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings.

  An embodiment of the present invention will be described with reference to FIGS. In this embodiment, as an image processing apparatus, a copy function, a facsimile (FAX) function, a print function, a scanner function, and an input image (a document image read by a scanner function or an image input by a printer or a FAX function) are distributed. The present invention is applied to an electrophotographic color copying apparatus 1 called a so-called MFP (Multi Function Peripheral).

  FIG. 1 is a system configuration diagram when a color copying apparatus 1 to which an image processing apparatus of the present invention is applied is connected. As shown in FIG. 1, each color copying apparatus 1 is connected via a LAN cable 1000 so that data can be transmitted and received. Such a color copying apparatus 1 serves as a child color copying apparatus when connected to another color copying apparatus 1. Specifically, in order to copy a large number of originals that exist in only one copy in a short time, the original is read by the scanner unit 300 of one color copying apparatus 1, and another color copy in which the read original image data is connected. Each of the color copying apparatuses 1 transmits to the apparatus 1 and performs image processing, and at the same time, the printer unit 100 has a connected output function of performing print output.

  In such a case, due to variations in the spectral sensitivity of the CCD of the scanner unit of each color copying apparatus 1, variation in the spectral sensitivity of the infrared cut filter for removing infrared light components, deterioration of the scanner optical system over time, etc. There is a machine difference in the read value of the image data, and the image signal output even when the same color original is read is different for each scanner unit 300 of each color copying apparatus 1, and as a result, the color output on the display and the printed color are different. There is. In order to solve such a problem, the present invention makes it possible to set image processing parameters for the purpose of reducing machine differences in the scanner unit 300 of each color copying apparatus 1, improving printer adjustment accuracy, and reducing adjustment variations. It is. This will be described in detail below.

  FIG. 2 is a front view of a schematic configuration of a main part of the electrophotographic color copying apparatus 1. 2, the color copying apparatus 1 includes a printer unit 100 as an image forming unit, a paper feeding unit 200, a scanner unit 300 as an image reading unit, and the like inside a main body housing 2. Contact glass 3 is disposed on the upper surface of 2. The color copying apparatus 1 has an ADF (Auto Document Feeder) 400 disposed on the top thereof. The ADF 400 separates a plurality of documents G set on the document table 401 one by one, and a roller and a document. The conveyance belt 402 conveys the document G to the document reading position by the scanner unit 300 on the contact glass 3, and the document G that has been read is discharged by a document conveyance belt 402 onto a discharge tray (not shown).

  The paper feeding unit 200 includes a paper feeding tray 201, a reversing unit 202, a conveyance roller (not shown), and the like, and separates a plurality of transfer sheets (transfer materials) P in the paper feeding tray 201 one by one. To the unit 100. The reversing unit 202 reverses the front and back surfaces of the transfer paper P on which the image has been formed by the printer unit 100 and sends it again to the printer unit 100 to form an image on the back surface. In addition, a paper feed tray 203 on which the transfer paper P is manually set is provided on one side surface of the main body housing 101. The paper feed unit 200 also transfers the transfer paper P on the paper feed tray 203. It is conveyed to the printer unit 100.

  A paper discharge tray 204 is disposed on the side surface of the main body casing 101 opposite to the paper feed tray 203, and the transfer paper P on which image formation has been completed by the printer unit 100 is placed on the paper discharge tray 204. It is discharged sequentially.

  The printer unit 100 is provided at a substantially central portion inside the main body housing 2, and an annular intermediate transfer belt 101 is disposed in a substantially diagonal direction in the vertical direction over a predetermined length at the central portion of the printer unit 100. The intermediate transfer belt 101 is stretched between a driving roller 102 and a transfer roller 103 and is driven to rotate clockwise as indicated by an arrow in FIG. 2, and black (K) and yellow (Y) along the intermediate transfer belt 101. In addition, organic photoconductor (OPC) drums 104K to 104C of φ30 [mm] as a total of four image carriers of three colors of magenta (M) and cyan (C) are disposed. Around the photosensitive drums 104K to 104C, the chargers 105K to 105C for charging the surfaces of the photosensitive drums 104K to 104C and the surfaces of the uniformly charged photosensitive drums 104K to 104C are irradiated with laser light. A laser optical system 106 for forming an electrostatic latent image, a black developing unit 107K for supplying each color toner to the electrostatic latent image and developing the toner image for each color, and Y (yellow), M (magenta), C (Cyan) three color developing units 107Y, 107M, and 107C, bias rollers 108K to 108C for applying a transfer voltage to the intermediate transfer belt 101, and the surfaces of the photosensitive drums 104K to 104C after being transferred, although not labeled. A cleaning device for removing residual toner, and electric power remaining on the surfaces of the photosensitive drums 104K to 104C after transfer. Discharger or the like are sequentially arranged to eliminate.

  The printer unit 100 uniformly charges the photosensitive drums 104K to 104C rotated in the counterclockwise direction by the charging chargers 105K to 105C, and applies the color of each color to the uniformly charged photosensitive drums 104K to 104C. A laser beam modulated with data is irradiated from the laser optical system 106 to form an electrostatic latent image, and each of the photosensitive drums 104K to 104C on which the electrostatic latent image is formed is developed by each color developing unit 107K to 107C. Toner is supplied to form a toner image. The printer unit 100 applies a transfer voltage to the intermediate transfer belt 101 by the bias rollers 108K to 108C, and sequentially superimposes and transfers the toner images of the respective colors on the photosensitive drums 104K to 104C to the intermediate transfer belt 101. Transfer a full color toner image.

  In the printer unit 100, a pressure roller 109 is disposed at a position facing the transfer roller 103 with the intermediate transfer belt 101 interposed therebetween, and a transfer from the paper supply unit 200 is performed between the pressure roller 109 and the transfer roller 103. The paper P is conveyed. A conveyance roller 110 and a registration roller 111 are disposed on the conveyance path of the transfer paper P to the pressure roller 109 and the transfer roller 103. The conveyance roller 110 transfers the transfer paper P from the paper feeding unit 200 to the registration roller. Then, the registration roller 111 conveys the transferred transfer paper P between the pressure roller 109 and the transfer roller 103 by adjusting the timing with the toner image on the intermediate transfer belt 101.

  The transfer roller 103 applies a transfer voltage to the intermediate transfer belt 101 to transfer the toner image on the intermediate transfer belt 101 onto the transfer paper P conveyed between the pressure roller 109.

  In the printer unit 100, a conveyance belt 112 and a fixing unit 113 are disposed on the downstream side in the conveyance direction of the transfer paper P on which the transfer of the toner image is completed. The toner image is transferred and separated from the intermediate transfer belt 101. The transfer paper P is transported to the fixing unit 113 by the transport belt 112. The fixing unit 113 includes a fixing roller 114 that is heated to a fixing temperature and a pressure roller 115 that is in pressure contact with the fixing roller 114, and the fixing roller 114 and the pressure roller 115 that are driven to rotate the transfer sheet P that has been conveyed. Then, the toner image on the transfer paper P is fixed to the transfer paper P and discharged onto a paper discharge tray 204 provided on the side surface of the main body housing 2.

  As shown in an enlarged view in FIG. 3, the scanner unit 300 reflects the light from the halogen lamp 302 provided with the lamp shade 301 and the original G or the halogen lamp 302 to the original G or a white reference plate (not shown). A first traveling body 305 equipped with a first mirror 303 and a second mirror 304 that reflects light reflected from the original G and the white reference plate, a third mirror 306 that sequentially reflects light reflected by the second mirror 304, and a second mirror 306. The first traveling body 305 includes a second traveling body 308 equipped with four mirrors 307, two switchable infrared cut filters 309 and 310, a lens 311 and a CCD (Charge Coupled Device) 312 as a photoelectric conversion element. And the second traveling body 308 are moved to the original G on the contact glass 3 while moving in the sub-scanning direction (direction indicated by an arrow a in FIG. 3) at a predetermined moving speed. Reading light is emitted from the halogen lamp 302 on the first traveling body 305, and reflected light from the original G is reflected by the second mirror 304 to the third mirror 306 on the second traveling body 308. The scanner unit 300 reflects the reflected light from the second mirror 304 with the third mirror 306 in the direction of the fourth mirror 307, and reflects the reflected light with the fourth mirror in the direction of the infrared cut filters 309 and 310. Infrared light is cut by the infrared cut filter 309 or the infrared cut filter 310 located on the road and is incident on the lens 311. The scanner unit 300 condenses incident light on the CCD 312, and the CCD 312 photoelectrically converts the incident light to read an image of the original G and output it as an analog image signal.

  As shown in FIG. 4, the color copying apparatus 1 is provided with an operation unit 500 on the upper surface of the main body housing 2. The operation unit 500 includes a start key 501, a clear / stop key 502, a numeric keypad 503, An interrupt key 504, a memory call key 505, a preheat / mode clear key 506, a color adjustment / registration key 507, a program key 508, an option key 509, an area processing key 510, a liquid crystal screen 511, and the like are provided.

  The control system of the color copying apparatus 1 is configured as shown in FIG. 5, and a CPU (system controller 600) that controls each part of the color copying apparatus 1 to execute processing as the color copying apparatus 1 ( Central Processing Unit) 601, ROM (Read Only Memory) 602 for storing various programs and data, RAM (Random Access Memory) 603 used as a work memory of the CPU 601, interface I / O 604 for connecting the CPU 601 and various circuit units, Various sensor control unit 605, power supply / bias control unit 606, drive control unit 607, operation control unit 608, communication control unit 609, storage device control unit 610, storage device 611, IPU 612, laser optical system drive unit 613, toner supply circuit 614 and the like.

  The various sensor control unit 605 includes a toner density sensor 615 installed in each of the YMCK developing units 107K to 107C, an optical sensor 616a to 616c installed in each of the YMCK image forming units 107K to 107C, a potential sensor 617, and an environment. Sensors 618 and the like are connected, and sensor signals from these sensors 615 to 618 are output to the CPU 601 via the interface I / O 604. The optical sensor 616a is disposed to face each of the photosensitive drums 104K to 104C, and detects the amount of toner adhered on the photosensitive drums 104K to 104C. The optical sensor 616b is disposed in the vicinity of each of the photosensitive drums 104K to 104C so as to face the intermediate transfer belt 101, and detects the toner adhesion amount on the intermediate transfer belt 101. The optical sensor 616 c is disposed to face the conveyance belt 112 and detects the amount of toner attached on the conveyance belt 112. In practice, detection may be performed at any one of the optical sensors 616a to 616c.

  The optical sensor 616a is arranged outside the image area in the axial direction of the photosensitive drums 104K to 104C and in the vicinity of the image area, and includes a light emitting element such as a light emitting diode and a light receiving element such as a photosensor. The toner adhesion amount in the toner image of the detection pattern latent image formed on the photosensitive drums 104K to 104C and the toner adhesion amount on the background portion are detected for each color, and the so-called residual after the neutralization of the photosensitive drums 104K to 104C. The potential is detected and detection signals are output to various sensor control units 605. Based on the detection signal from the optical sensor 616a, the various sensor control units 605 obtain a ratio between the toner adhesion amount in the detection pattern toner image and the toner adhesion amount in the background portion, and compare the ratio value with a reference value. A change in the image density is detected, and the control value of the toner density sensor 615 for each color of YMCK is corrected. In practice, the optical sensor 616a is not necessarily provided in each of the photosensitive drums 104K to 104C, and may be detected by any one of the photosensitive drums 104K to 104C.

  The toner concentration sensor 615 is disposed in each of the developing units 107K to 107C, detects the toner concentration based on a change in magnetic permeability of the developer present in the developing units 107K to 107C, and controls the detection signal with various sensors. Output to the unit 605. When the various sensor control units 605 compare the detected toner density value with the reference value based on the detection sensor from the toner density sensor 615 and determine that the toner density falls below a certain value and the toner is in an insufficient condition, A toner supply signal having a magnitude corresponding to the shortage is output to the toner supply circuit 614. The toner supply circuit 614 supplies toner to the corresponding developing units 104K to 104C based on the toner supply signal.

  The potential sensor 617 detects the surface potential of each of the photosensitive drums 104 </ b> K to 104 </ b> C, which are image carriers, and outputs detection signals to various sensor control units 605.

  The power source / bias control unit 606 controls the supply of power to the developing units 107K to 107C and the power circuit 619. The power circuit 619 supplies a predetermined charging discharge voltage to the charging chargers 105K to 105C, and the developing units 107K to 107K. A developing bias having a predetermined voltage is supplied to 107C, and a predetermined transfer voltage is supplied to the bias rollers 108K to 108C and the charging chargers 105K to 105C.

  The drive control unit 607 supplies toner to the laser optical system drive unit 613 that adjusts the laser output of the laser optical system 106, the intermediate transfer belt drive unit 620 that controls the rotational drive of the intermediate transfer belt 101, and the developing units 107K to 107C. The driving of the toner replenishing circuit 614 for performing the above is controlled. The operation control unit 608 performs the acquisition of the operation content in the operation unit 500, the lighting control of lamps and the like, the display control of the liquid crystal screen 511, and the like under the control of the CPU 601.

  A network such as the Internet or an intranet is connected to the communication control unit 609, and communication is performed via the network. The storage device 611 is configured by a hard disk or the like, and stores various types of information, particularly image data, under the control of the storage device control unit 610.

  Next, the IPU 612 will be described with reference to FIG. As shown in FIG. 6, the IPU 612 includes a shading correction circuit 701, an area processing unit 702, a scanner γ conversion unit 703, an image memory 704, an image separation unit 705, an I / F (interface) 706, and an MTF (Modulation Transfer Function) filter. 707, hue determination circuit 708, color conversion UCR (Under Color Removal) processing circuit 709, pattern generation unit (gradation pattern generation means) 710, scaling circuit 711, image processing circuit 712, image processing printer γ A conversion circuit (first image signal conversion means) 713, a gradation processing circuit (color conversion means) 714, a CPU 715, a ROM 716, a volatile RAM 717, a nonvolatile NV-RAM 719, and the like are provided. Connected by.

  The printer unit 100 includes an I / F selector 721, a pattern generation unit (tone pattern generation unit) 722, an image forming printer γ correction circuit (second image signal conversion unit) 723, and image formation of the printer unit 100. The printer engine 724 and the like that actually perform the above are provided.

  The CPU 715 is connected to the ROM 716 and the RAM 717 via a bus 718, and is connected to the system controller 600 through a serial I / F, and commands from the operation unit 500 and the like are transmitted through the system controller 600. The CPU 715 sets various parameters in necessary units of the IPU 612 based on the image quality mode, density information, region information, and the like transmitted from the operation unit 500 or the like.

  The scanner unit 300 color-separates the original G on the contact glass 3 into R, G, and B, for example, reads it with 10 bits, and outputs the read image signal of the original G to the shading correction circuit 701 of the IPU 612.

  The shading correction circuit 701 corrects unevenness in the main scanning direction of the image signal input from the scanner unit 300 and outputs the image signal to the scanner γ conversion unit 703 as an 8-bit signal, for example.

  The area processing unit 702 generates an area signal for distinguishing which area in the original G the image data currently being processed belongs to, and parameters used in subsequent image processing are switched by this area signal. . For each designated area, this area processing unit 702 includes a color correction coefficient, a spatial filter, Image processing parameters such as a gradation conversion table are set for each image area.

  The scanner γ conversion unit 703 converts the read signal from the scanner unit 300 from reflectance data to lightness data, and stores it in the image memory 704. The image memory 704 stores the image signal after the scanner γ conversion, and outputs it to the MTF filter 707 via the image separation unit 705 and the I / F 706. The image separation unit 705 determines the character part and the photographic part of the image of the document G and the chromatic / achromatic color, and outputs the determination result to the MTF filter 707.

  The MTF filter 707 responds to the edge degree of the image signal in addition to the process of changing the frequency characteristics of the image signal such as edge enhancement and smoothing according to the user's preference such as a sharp image or a soft image. Edge enhancement processing (adaptive edge enhancement processing). For example, the MTF filter 707 performs so-called adaptive edge enhancement on each of the R, G, and B signals, which performs edge enhancement on a character edge and does not perform edge enhancement on a halftone image.

Specifically, for example, as shown in FIG. 7, the MTF filter 707 includes a smoothing filter 730, an edge amount detection filter 731, a Laplacian filter 732, a smoothing filter 733, a table conversion 734, an accumulator 735, and an adder 736. Etc., and the smoothing filter 730 smoothes the image signal converted from the reflectance linearity to the lightness linearity by the scanner γ conversion unit 703 by using the coefficient shown below, and the Laplacian filter 732 is obtained as the image signal A. And output to the adder 736.

  Next, the 3 × 3 Laplacian filter 732 extracts a differential component of the image data by using a filter as shown in FIG. 8 and outputs it to the integrator 735 as an image signal B.

  Of the 10-bit image signal that is not subjected to γ conversion by the scanner γ conversion unit 703, for example, the upper 8-bit component is input to the edge amount detection filter 731. The edge amount detection filter 731 is illustrated in FIG. Edge detection by performing edge detection using the sub-scanning direction edge detection filter, the main scanning direction edge detection filter shown in FIG. 9-2 and the oblique direction detection filter shown in FIGS. 9-3 and 9-4. Among these, the maximum value is output to the smoothing filter 733 as the edge degree.

The smoothing filter 733 smoothes the edge degree detected by the edge amount detection filter 731 using, for example, the following coefficient as necessary, and the sensitivity difference between the even pixels and the odd pixels of the scanner unit 300 is smoothed. The influence is reduced and the result is output to the table conversion circuit 734.

  The table conversion circuit 734 converts the obtained edge degree into a table and outputs it as an image signal C to the integrator 735. In this case, the table conversion circuit 734 designates the density of lines and dots (including contrast and density) and the smoothness of the halftone dot portion according to the table values. An example of the table is shown in FIG. The edge degree becomes the largest with black lines or dots on a white background, and becomes smaller as the boundary between pixels becomes smoother as in finely printed halftone dots, silver halide photographs, thermal transfer originals, and the like.

  The accumulator 735 takes the product of the edge degree (image signal C) converted by the table conversion circuit 734 and the output value (image signal B) of the Laplacian filter 732 and outputs the product to the adder 736 as an image signal D. An adder 736 adds the smoothed image signal (image signal A) to the image signal D, and outputs the resultant signal as an image signal E to the hue determination circuit 708 and the color conversion UCR processing circuit 709, which are subsequent image processing circuits. .

  The color conversion UCR processing circuit 709 corrects the difference between the color separation characteristics of the input system and the spectral characteristics of the color material of the output system, and calculates the amount of the color material YMC necessary for faithful color reproduction; And a UCR processing unit for replacing a portion where three colors of YMC overlap with K (black). The color correction processing method will be described with reference to the color space diagrams of FIGS.

  As shown in FIG. 11, the color correction processing is performed by dividing the color space (R, G, B) on a plane extending radially around the achromatic color axis (R = G = B (≡N axis)). . Saturation changes along the T-axis provided perpendicular to the N-axis. Further, the hue changes along the rotation direction U about the N axis on a plane parallel to the T axis. That is, all the points on the surface formed in parallel with the N axis in the predetermined rotation direction U are color points indicating a hue determined by the rotation direction U.

  Points C, M, and Y are points where the saturation is maximum in CMY, which is the primary color of the printer. Points R, G, and B are points where the saturation is maximum in RGB, which is the secondary color of the printer. The printer color reproduction region 672 is a substantially spherical region formed by connecting these points C, M, Y, R, G, and B, and points W and K with curves. That is, the inside of the printer color reproduction area 672 is a color area that can be output by the printer. The signal color region 660 is a color region that can be taken by the signal color for the color image signal.

  Note that the image processing apparatus regards the printer color reproduction area 670 as the printer color reproduction area 672 in order to simplify processing when correcting the signal color in this color space. Here, the printer color reproduction region 670 is a dodecahedron-like region formed by connecting points C, M, Y, R, G, B, points W and K corresponding to the maximum values of eight colors with straight lines. It is. In this way, since the printer color reproduction area 670 is regarded as the printer color reproduction area 672, no substantial error occurs in the correction amount X.

  Next, the hue area will be described with reference to FIGS. 12 and 13 show a color space divided into a plurality of hue regions. The C boundary surface 633 is a plane determined by the points C, W, and K. Similarly, i boundary surfaces 634 to 638 (i = M, Y, R, G, B) are planes determined by points i, W, K (i = M, Y, R, G, B), respectively. . The color space is divided by these boundary surfaces 633 to 638. In the color space divided by the boundary surfaces 633 to 638, a CB hue region 640, a BM hue region 641, an MR hue region 642, an RY hue region 643, a YG hue region 644, and a GC hue region 645 are formed.

  Next, a hue determination method for image data by the hue determination circuit 708 will be described. First, a method for determining hue in a three-dimensional space will be described, and then a method for determining hue in a two-dimensional color plane will be described.

  In the hue determination of the three-dimensional space, each hue evaluation value Fx is calculated from the image data, and the hue area code of the hue area including the signal color is determined based on the hue evaluation value Fx.

Here, a theoretical derivation method of the hue evaluation value Fx will be described. The color coordinates indicating the points C, M, Y, R, G, B, W, and K shown in FIG. 11 are respectively (Dir, Dig, Div) (i = c, m, y, r, g, b, w). , K)
I will show that. For example, the color coordinates corresponding to the point C are (Dcr, Dcg, Dcb). In this case, for example, the C boundary surface 633 is expressed by Equations 1 to 6 shown below.

  For example, the color space is divided by the boundary surface 633 into two regions, a region including the CB hue region 640 and a region including the GC hue region 645. Similarly, the color space is divided into two regions by each boundary surface 634-638. Therefore, in which hue region the color image signal is included can be determined based on which region of the two regions formed by the boundary surfaces 633 to 638 is included in the color image signal. . That is, based on the sign of the value obtained by substituting the color image signal (Dr, Dg, Db) for each of Equations 1 to 6, a hue region including the color image signal can be determined. Therefore, the hue evaluation value Fx is determined based on Formulas 1 to 6. That is, the left sides of Equations 1 to 6 are Fc, Fm, Fy, Fr, Fg, and Fb, respectively.

Therefore, in the hue determination in the three-dimensional space, each hue evaluation value Fx defined in the following Expressions 7 to 12 is calculated.

For example, when Fc and Fg calculated from an arbitrary point (Dr, Dg, Db) in the color space satisfy “Fc ≦ 0 and Fb> 0”, this point is included in the CB hue region. It can be seen from the table shown in.
Thus, each hue region is defined by the hue evaluation value Fx. That is, the condition of the hue evaluation value Fx associated with the hue area code in the hue area code table shown in Table 3 is a condition determined from the above formula.

  In the hue area code table shown in Table 3, the color coordinates on the N-axis are included in the GC hue area for convenience, but may be included in other hue areas. The hue evaluation value Fx varies depending on the actual value of (Dir, Dig, Div) (i = c, m, y, r, g, b, w, k). Therefore, the condition of the hue evaluation value to be associated with each hue area code in the hue area code table (Table 3) may be changed according to the value of the hue evaluation value.

  Next, a method for mapping a three-dimensional color space to a two-dimensional plane and using the color coordinates of the color image signal in the two-dimensional plane to determine a hue area including the color image signal is shown in FIG. The operation of the hue determination circuit 708 will be described based on the flowchart of FIG.

In the flowchart shown in FIG. 15, first, when a color image signal is input to the hue determination circuit 708, the value of the color image signal is two-dimensionalized (S251). That is, the difference GR and the difference BG are obtained by substituting the value of the color image signal into the following equation.
GR = Dg−Dr (13)
BG = Db−Dg (14)
As a result, values (Dr, Dg, Db) in the color space of the color image signal are converted into values (GR, BG) in the color plane.

  FIG. 14 shows a two-dimensional plane on which a color image signal is to be mapped. In this two-dimensional plane, a straight line corresponding to “Dg−Dr” is a GR axis, and a straight line corresponding to “Db−Dg” is a BG axis. The GR axis and the BR axis are orthogonal to each other.

The points (Dr, Dg, Db) on the color space are mapped to the color plane shown in FIG. Further, the point (Dnr, Dng, Dnb) on the N axis in the color space is mapped to the point (Dng-Dnr, Dnb-Dng) on the color plane shown in FIG. Since Dnr = Dng = Dnb, Equation 15 shown below is obtained.
(Dng−Dnr, Dnb · Dng) = (0, 0) (15)

  That is, all points on the N axis are mapped to the origin n on the plane shown in FIG. Further, the points C, M, Y, R, G, and B in the color space are arranged around the origin n as shown in FIG. Accordingly, the six hue regions 640 to 645 shown in FIG. 12 are mapped to regions 740 to 745 divided by straight lines connecting the N axis and the points C, M, Y, R, G, and B on the color plane. Is done.

  Next, the difference GR, the difference BG, and each hue evaluation value Fx ′ (x = c, m, y, r, g, b) are calculated from the values of each color of the input color image signal (S252). Based on the hue evaluation value Fx ′, the difference GR, and the difference BG, the hue area code of the hue area including the signal color is determined using the hue area code table shown in Table 4 below (S253).

A method for deriving the hue evaluation value Fx ′ will be described. In the color plane shown in FIG. 14, the straight line connecting point N and points C, M, Y, R, G, and B, that is, straight line NC, straight line NM, straight line NY, straight line NR, straight line NG, and Each straight line NB is expressed as follows.
From the magnitude relationship between the BG value obtained by substituting the GR value of the color image signal into each of Expressions 16 to 21, and the BG value of the actual color image signal, the straight line determined by each expression and the color image signal You can see the positional relationship with the corresponding points. Accordingly, in which hue region the color image signal is included depends on the magnitude relationship between the BG value obtained by substituting the GR value of the color image signal into Equations 16 to 21 and the BG value of the color image signal. Based on this, it can be determined.

Therefore, the hue evaluation value Fx ′ is determined based on Expressions 16 to 21 as follows.
That is, in Expressions 16 to 21, the left sides of Expressions 16 to 21 are Fc ′, Fm ′, Fy ′, Fr ′, Fg ′, and Fb ′, respectively.

For example, when Fc ′ and Fb ′ calculated from an arbitrary point (GR, BG) in the color plane satisfy “BG ≦ Fc ′ and BG> Fb ′”, this point is included in the CB hue region. Can be seen from the table shown below.
That is, the condition of the hue evaluation value Fx ′ associated with the hue area code in the hue area code table shown in Table 4 is a condition determined from the above formula. Thus, the condition of the hue evaluation value Fx ′ is set in advance in the hue area code table of Table 4. Therefore, the hue determination circuit 708, as in the hue area code table of Table 4, satisfies the conditions that the BG and the hue evaluation value Fx ′ satisfy from the conditions of the hue evaluation values Fx ′ associated with each hue area code. And the hue area code associated with this condition may be selected in the hue area code table (Table 4). FIG. 16 is a color plan view of FIG. 14 corresponding to the hue region.

  In the hue area code table shown in Table 4, the color coordinates on the N-axis are included in the GC hue area, but may be included in other hue areas.

  Further, the hue evaluation value Fx ′ varies depending on the actual value of (Dir, Dig, Div) (i = c, m, y, r, g, b, w, k). Therefore, the condition of the hue evaluation value to be associated with each hue area code in the hue area code table (Table 4) may be changed according to the value of the hue evaluation value Fx ′.

Although the color image signals (Dr, Dg, Db) are converted into values (GR, BG) in the color plane by the conversion formulas shown in Formulas 13 to 14, instead of this, the following conversion formulas (28 ) (29).
GR = Ri · Dr + Gi · Dg + Bi · Db (28)
BG = Rj · Dr + Gj · Dg + Bj · Db (29)
here,
Ri = Gi = Bi = 0, Rj = Gj = Bj = 0
It is.

As described above, the hue determination circuit 708 determines where the input image signal (R, G, B) belongs to the divided space, and then masks set in advance for each space. Using the coefficient, color correction processing is performed using the following equation (30) (color correction means).
At that time, linear processing of the masking coefficient is performed as necessary, such as density adjustment and color balance adjustment. In the following, the dividing point is a point where a boundary surface and a side intersect, for example, a point G (Green) in FIG. As an example, when the hue hue is G (Green), the following equation (31) is obtained.

  Here, the left side P (hue) (P = C, M, Y, K; hue = hue R, G, B, Y, M, C, K, W etc) is the printer vector, and the right side S (hue) (S = B, G, R; hue = hue R, G, B, Y, M, C, K, W etc) as a scanner vector, aPS (hue) (P = C, M, Y, K; S = B, G, R) is called a linear masking coefficient for each hue.

Normally, the linear masking coefficient aPS (hue) (P = Y, M, C, K; S = R, G, B, constant) in each space is two different points on the achromatic axis as shown in FIG. R1, G1, B1) and (R2, G2, B2) and two points (R3, G3, B3) and (R4, G4, B4) on the two boundary surfaces that are not on the achromatic axis. , G, B values and recording values (C1, M1, Y1, K1), (C2, M2, Y2, K2), (C3, M3, (Y3, K3) and (C4, M4, Y4, K4) are determined in advance and obtained by the following calculation.
This equation 32 is
Against
Is the inverse of
The two sides are swapped.

  Here, aXY (3-4) represents a masking coefficient formed in a color region between hue 3 and hue 4, and the recorded values of C, M, Y, and K at each point are before UCR (under color removal). Equivalent achromatic color density conversion value.

In the following, in order to simplify the description, two points on the achromatic color axis are set as a white point and a black point. In this case, if the maximum value acquired by the equivalent achromatic color density conversion value is Xmax, each value has the following relationship.
In the case of a white dot R1 = G1 = B1 = C1 = M1 = Y1 = 0 ≧ K1
In the case of a black dot R1 = G1 = B1 = C1 = M1 = Y1 = Xmax ≧ K2

Further, two points on the boundary surface are points where the minimum value of the recording values of the developing portions C, M, Y, and K is 0 and the maximum value of the recording value is Xmax, that is, recording is possible on each boundary surface. The point with the highest saturation is good. That is,
Min (C3, M3, Y3) = 0 ≧ K3
Max (C3, M3, Y3) = Xmax
Min (C4, M4, Y4) = 0 ≧ K4
Max (C4, M4, Y4) = Xmax
Is established.

Further, the UCR rate can be controlled by determining the recording value of the developing unit K from the minimum value of the developing units C, M, and Y as follows, for example.
When UCR rate is 100%: K = Min (C, M, Y)
When the UCR rate is 70%: K = Min (C, M, Y) × 0.7

  As shown in FIG. 11, when the color space (R, G, B) is divided by six boundary surfaces, a total of eight R points, at least six points on each boundary surface and two points on the achromatic color axis. , G, and B values, and C, M, Y, and K recording values of the developing unit that are optimal for color reproduction are determined in advance, and a masking coefficient for each space is obtained based on these values. As described above, the masking coefficient of each space is obtained in advance and stored in ROM, RAM, etc., and in the color correction process, an appropriate masking coefficient is selected according to the color determined in the hue determination, and color correction is performed. It can be performed.

On the other hand, the color conversion UCR processing circuit 709 performs color correction processing by calculating using the following equation.
Y ′ = Y−α · min (Y, M, C)
M ′ = M−α · min (Y, M, C)
C ′ = C−α · min (Y, M, C)
Bk = α · min (Y, M, C)
In the above equation, α is a coefficient that determines the amount of UCR, and when α = 1, 100% UCR processing is performed. α may be a constant value. For example, when α is close to 1 in the high density portion and close to 0 in the highlight portion (low image density portion), the image in the highlight portion can be smoothed.

  The masking coefficient is changed to 12 hues obtained by further dividing the 6 hues of RGBYMC into 2 parts and further to every 14 hues of black and white.

  The hue determination circuit 708 determines to which hue the image data read by the scanner unit 300 belongs, and outputs the determination result to the color conversion UCR processing circuit 709.

  The color conversion UCR processing circuit 709 selects the masking coefficient for each hue based on the determination result of the hue determination circuit 708 and performs the color correction process.

  A scaling circuit 711 performs vertical / horizontal scaling on the image data for which color correction processing has been completed, and an image processing (creating) circuit 712 performs repeat processing or the like on the image data for which scaling processing has been completed. The data is output to the processing printer γ conversion circuit 713.

  The image processing printer γ conversion circuit 713 corrects the image signal according to the image quality mode such as characters and photographs, and can simultaneously perform background skipping. The image processing printer γ conversion circuit 713 has a plurality of (for example, 10) gradation conversion tables (image signal conversion tables) that can be switched in accordance with the area signal generated by the image processing circuit 712. Select the optimum gradation conversion table for each original such as text, silver halide photograph (printing paper), printed original, inkjet, highlighter pen, map, thermal transfer original, etc. from multiple image processing parameters and enter the image quality mode The corresponding image signal is corrected and output to the gradation processing circuit 714.

  The gradation processing circuit 714 performs dither processing on the image data input from the image processing printer γ conversion circuit 713 and outputs the result to the interface selector 721 of the printer unit 100.

  The gradation processing circuit 714 can select dither processing of any size from 1 × 1 no dither processing to dither processing consisting of m × n pixels (m and n are positive integers), for example, up to 36 pixels Up to dither processing using the pixels. The dither size using all 36 pixels is, for example, a total of 36 pixels of 6 pixels in the main scanning direction × 6 pixels in the sub scanning direction, or a total of 36 pixels of 18 pixels in the main scanning direction × 2 pixels in the sub scanning direction. There is.

  The printer unit 100 is connected to the IPU 612 by the I / F selector 721 as described above, and the I / F selector 721 processes the image data read by the scanner unit 300 with an external image processing apparatus or the like. Therefore, the printer unit 100 has a switching function for outputting or outputting the image data from the external host computer 740 or the image processing apparatus by the printer unit 100. Note that image data from the external host computer 740 is input to the I / F selector 721 via the printer controller 741.

  An image forming printer γ (process control γ) γ correction circuit 723 converts an image signal from the I / F selector 721 using a gradation conversion table (image signal conversion table), and performs laser modulation of the printer engine 724. Output to the circuit.

  In the color copying apparatus 1, as described above, the image signal from the host computer 740 is input to the I / F selector 721 through the printer controller 741, the gradation is converted by the image forming printer γ correction circuit 723, and the printer engine By performing image formation in 724, the printer can be used as a printer.

  The color copying apparatus 1 executes the image processing by controlling each part of the IPU 612 while the CPU 715 uses the RAM 717 as a work memory based on the program in the ROM 716, and the CPU 715 performs the above-described image processing through the serial I / F. When a command such as an image quality mode, density information, and area information is transmitted from the operation unit 500 or the like through the system controller 600, the IPU 612 is connected based on the image quality mode, density information, area information, and the like. Various parameters are set in and image processing is performed.

  The pattern generation unit 710 of the IPU 612 and the pattern generation unit 722 of the printer unit 100 generate gradation patterns used by the IPU 612 and the printer unit 100, respectively.

  In addition, as described above, the area processing unit 702 generates an area signal for distinguishing which area in the document G the image data currently being processed belongs to, and based on this area signal, the subsequent image is generated. Although parameters used in the processing are switched, the concept of area processing of the area processing unit 702 can be illustrated as shown in FIG. That is, in FIG. 17, an area corresponding to image data obtained by reading a document G having a plurality of areas such as a character area (area 0), a photographic paper area (area 1), and an inkjet area (area 2) with the scanner unit 300 is displayed. The processing unit 702 compares the designated area information (region information) on the document G with the reading position information at the time of image reading, and generates an area signal. As shown in FIG. 17 for the image processing printer γ conversion circuit 713 and the gradation processing circuit 714, the IPU 612 is based on the area signal from the area processing unit 702, the scanner γ conversion unit 703, the MTF filter 707, and the color conversion. Parameters used in the UCR processing circuit 709, the image processing circuit 712, the image processing printer γ conversion circuit 713, and the gradation processing circuit 714 are changed.

  For example, the image processing printer γ conversion circuit 713 decodes the area signal from the area processing unit 702 with a decoder, and a selector (character (table 1), inkjet (table 2), photographic paper (table 3), and printing (print ( Select from a plurality of gradation conversion tables such as Table 4). In the document G of FIG. 17, an example in which a character region 0, a photographic paper region 1, and an inkjet region 2 are present is illustrated. The image processing printer γ conversion circuit 713 performs the processing for the character region 0. Thus, the gradation conversion table 1 for characters, the gradation conversion table 3 for photographic paper for the photographic paper region 1, and the gradation conversion table 2 for inkjet for the region 2 of the inkjet. select.

  The gradation processing circuit 714 performs processing that does not use dither by the selector 2 based on a signal obtained by decoding the area signal again by the decoder with respect to the image signal subjected to gradation conversion by the image processing printer γ conversion circuit 713. Of the gradation processing such as dithering and error diffusion processing, the gradation processing to be used is switched. Note that the gradation processing circuit 714 performs error diffusion processing on the inkjet document G and the inkjet region of the document G.

  The gradation processing circuit 714 selects whether the image signal after gradation processing is the line 1 or the line 2 based on the reading position information by the decoder. The selection is switched every time one pixel differs in the sub-scanning direction. The gradation processing circuit 714 temporarily stores the data of the line 1 in a FIFO (First In First Out) memory located downstream of the selector, and outputs the data of the line 1 and the line 2 to thereby change the pixel frequency. The signal is reduced to 1/2 and output to the I / F selector 721.

  The color copying apparatus 1 includes a laser modulation circuit 120 as shown in FIG. 18 in the laser optical system 106 of the printer unit 100, and includes a look-up table (LUT) 121, a pulse width modulation circuit (PWM). 122, a power modulation circuit (PM) 123, and the like. The writing frequency in the laser modulation circuit 120 is 18.6 [MHz], and the scanning time of one pixel is 53.8 [nsec].

  The look-up table (LUT) 121 receives 8-bit image data, and the look-up table (LUT) γ-converts the input image data and outputs it to the pulse width modulation circuit (PWM) 122. The pulse width modulation circuit (PWM) 122 converts an 8-bit image signal input from the look-up table (LUT) 121 into an 8-value pulse width and converts it into a power modulation circuit (PM). ) 123, and the power modulation circuit (PM) 123 performs 32-level power modulation with the lower 5 bits. A laser diode (LD) 124 and a photodetector (PD) 125 are connected to the power modulation circuit (PM) 123, and the power modulation circuit (PM) 123 is based on a signal obtained by modulating the laser diode (LD) 124. While emitting light, the emission intensity of the laser diode (LD) 124 is monitored based on a monitor signal from the photodetector (PD) 125, and correction is performed for each dot. The maximum value of the intensity of the laser beam emitted from the laser diode (LD) 124 can be varied to 8 bits (256 levels) independently of the image signal.

Further, the beam diameter in the main scanning direction with respect to the size of one pixel of the laser beam emitted from the laser diode (LD) 124 (the width when the intensity of the stationary beam is attenuated to 1 / e ² with respect to the maximum value) Defined) is 600 DPI, one pixel 42.3 [μm], the main scanning direction 50 [μm] and the sub-scanning direction 60 [μm] are used.

  The laser modulation circuit 120 is prepared corresponding to each of the image data of line 1 and line 2 described with reference to FIG. 17, and the image data of line 1 and line 2 are synchronized, and the photosensitive drum 104K to 104C are scanned in parallel in the main scanning direction.

  Next, as shown in FIG. 19, the scanner unit 300 has a circuit block configuration, and the CCD 312, the amplifier circuit 321, the S / H (sample hold) circuit 322, the A / D conversion circuit 323, and the black correction circuit 324. A CCD driver 325, a pulse generator 326, a clock generator 327, and the like.

  The scanner unit 300 irradiates the original G with the halogen lamp 302 shown in FIG. 3, and color-reflects the reflected light from the original G by the RGB filter of the CCD 312, reads the image of the original G with the CCD 312, and Are output to the amplifier circuit 321. The CCD driver 325 supplies a pulse signal for driving the CCD 312, and a pulse source necessary for driving the CCD driver 325 is generated by a pulse generator 326. The pulse generator 326 generates a pulse signal using the clock signal oscillated by the clock generator 327 made of a crystal oscillator or the like as a reference signal, and is necessary for the S / H circuit 322 to sample and hold the image signal from the CCD 312. A timing signal is supplied to the S / H circuit 322.

  The amplifier circuit 321 amplifies the analog image signal from the CCD 312 to a predetermined level and outputs it to the S / H circuit 322. The S / H circuit 322 samples and holds the image signal from the amplifier circuit 321 to perform A / The data is output to the D conversion circuit 323. The A / D conversion circuit 323 digitizes the analog image signal sampled and held by the S / H circuit 322, for example, into an 8-bit signal, and outputs it to the black correction circuit 324. The black correction circuit 324 For image data digitally converted by the conversion circuit 323, variation in black level (electric signal when the amount of light is small) between chips of the CCD 312 and between pixels is reduced, and streaks and unevenness occur in the black portion of the image. Is output to the shading correction circuit 701 of the IPU 612.

  As described above, the shading correction circuit 701 corrects the white level (electric signal when the amount of light is large), and moves the white level to the position of the uniform white reference plate as shown in FIG. Based on the white data at the time of irradiation, correction is performed by correcting variations in sensitivity of the irradiation system, optical system, and CCD 312.

  The image signal from the shading correction circuit 701 is processed by the image processing unit from the area processing unit 702 to the gradation processing circuit 714 of the IPU 612 and is recorded and output by the printer unit 100. The circuits 715 are controlled by the CPU 715 based on programs and data in the ROM 716 and the RAM 717.

  The amplification amount of the amplifying circuit 321 is determined so that the output value of the A / D conversion circuit 323 becomes a desired value with respect to a specific document density. A value of 0.05 (reflectance: 0.891) is obtained as 240 values with 8-bit signal values, and at the time of shading correction, the gain is lowered to increase the sensitivity of shading correction. The reason for this is that with an amplification factor during normal copying, if there is a large amount of reflected light, an 8-bit signal that exceeds 255 values will saturate to 255 values, resulting in errors in shading correction. This is because it occurs. That is, FIG. 21 is a schematic diagram in which the read signal of the image amplified by the amplifier circuit 321 is sampled and held by the S / H circuit 322, and the horizontal axis represents the amplified analog image signal through the S / H circuit 322. The passing time and the vertical axis represent the magnitude of the amplified analog signal. The analog signal is sampled and held at a predetermined sample and hold time shown in FIG. 21, and the signal is sent to the A / D conversion circuit 323. FIG. 21 is an image signal obtained by reading the white level. The amplified image signal is, for example, 240 values as a value after A / D conversion at the time of copying, and 180 values at the time of white correction. An example of a signal is shown.

  Next, the operation of the present embodiment will be described. The color copying apparatus 1 according to the present embodiment executes scanner calibration described below at least once in advance when using the above-described connection output function.

  Scanner calibration is performed, for example, using a connected color correction chart HC that is a calibration reference chart as shown in FIG. This connected color correction chart HC is originally a color patch (color patch) portion which is a plurality of chromatic patches having different hue regions formed with a plane provided in parallel in the color space in parallel to the lightness axis. Although it is drawn in color, in FIG. 22, it is displayed in black and white indicating the difference in color with different hatching as a patent drawing.

In the connected color correction chart HC, as shown in FIG. 22, gray patches (black patches), which are achromatic colors and different image densities, are arranged on a recording medium such as paper. It is a patch chart in which a plurality of chromatic color patches having different hues are arranged on the left and right. The two achromatic gray patches in the center are composed of a gradation pattern printed on one side with 3C gray (a color obtained by overlaying YMC), and the other on a gradation pattern printed with a single black ink color. That is, the connected color correction chart HC is in the main scanning direction of the scanner unit 300.
White 1 (background), color 1, black 1, black 2, color 2, white 2 (background)
It is arranged. By arranging the color patch between the white (background) and the black patch in this way, it is possible to reduce the influence of flare light from surrounding patches (particularly the black patch). In contrast, for example,
White 1 (background), black 1, color 1, black 2, color 2, white 2 (background)
Since the color 1 is affected by the black patches on both sides and the reading value of the scanner unit 300 becomes dark, the former arrangement is adopted to prevent this.

  Each patch of the connected color correction chart HC is formed about four times as large as a patch of an ACC pattern (see FIG. 43) used in ACC (automatic gradation correction) described later. The reason why the patch of the connected color correction chart HC is formed in this way is to reduce the influence of flare light (reflected light from the document surface around the patch) in the scanner unit 300.

  Furthermore, as shown in FIG. 22, the connected color correction chart HC is arranged with patches concentrated at a substantially central portion of the scanner unit 300 in the main scanning direction. The reason why the patches are concentrated in the central portion of the scanner unit 300 in the main scanning direction is that the end portion of the scanner unit 300 in the main scanning direction is often darker than the central portion. is there. The patch of the connected color correction chart HC is arranged at a position included in the reading range of the ACC pattern. This is to facilitate diversion from the ACC pattern reading control software when creating an application program.

The chromatic color patch is further divided from the 6 hues of YRMMBCG (Yellow, Red, Magenta, Blue, Cyan, Green), and 12 hues (Y, YR, R, RM, M, MB, B, BC, C, CG, G, GY) 12 colors corresponding to the hue division point of the 12 hue masking coefficient (for example, a color intermediate between Y and YR), Y for reference (for example, for copying and visual evaluation), 16 colors including G, R and Orange. The hue angle of each color patch in the connected color correction chart HC is such that the hue angle h ^* is 0 ≦ h ^* <360 ° [degree] with respect to the lightness L ^* , the saturation C ^* , and the hue h ^* . (Hereinafter abbreviated as [deg])
Yellow Red (h ^* = 1 [deg])
Orange (h ^* = 26 [deg])
Red Yellow (h ^* = 47 [deg])
Red (h ^* = 54 [deg])
Red Magenta (h ^* = 60 [deg])
Magenta Red (h ^* = 84 [deg])
Magenta Blue (h ^* = 95 [deg])
Blue Magenta (h ^* = 139 [deg])
Blue Cyan (h ^* = 170 [deg])
Cyan Blue (h ^* = 207 [deg])
Cyan Green (h ^* = 232 [deg])
Green Cyan (h ^* = 277 [deg])
Green (h ^* = 291 [deg])
Green Yellow (h ^* = 313 [deg])
Yellow Green (h ^* = 352 [deg])
Yellow (h ^* = 356 [deg])
It is. The numerical value is an example.

  In scanner calibration, the connected color correction chart HC shown in FIG. 22 is read, and based on the read result, a scanner γ conversion table is first created so as to correct the machine difference of the scanner unit 300.

  The execution procedure for creating the scanner γ conversion table in this scanner calibration is shown in the sequence diagram of FIG.

  First, when the user or service person selects various setting modes on the liquid crystal screen 511 of the operation unit 500 shown in FIG. 4, the color copying apparatus 1 displays various adjustment screens as shown in FIG. 24 on the liquid crystal screen 511. When execution of “scanner calibration” is selected on the various adjustment screens, the scanner calibration mode is entered, and a scanner calibration start screen as shown in FIG. 25 is displayed on the liquid crystal screen 511. . In this scanner / calibration mode, the user or service person places the connected color correction chart HC on the contact glass 3 as the document table, and displays “read” on the scanner / calibration start screen on the liquid crystal screen 511 shown in FIG. Press the “Start” key (S1 in FIG. 20).

  When there is an instruction to start reading the connected color correction chart HC from the operation unit 500, the color copying apparatus 1 causes the system controller 600 to send the connected color correction chart to the scanner unit 300 as shown by S2 in FIG. HC reading is instructed, and as shown by S3 in FIG. 23, the scanner unit 300 executes reading of the connected color correction chart HC, and obtains read values of RGB signals for the respective patches of the connected color correction chart HC. Acquired, and the reading value of the connected color correction chart HC is transmitted to the IPU 612 as indicated by S4 in FIG.

  On the other hand, as shown by S5 in FIG. 23, the reading reference value (reference data) of the connected color correction chart HC is read from the nonvolatile RAM (reference value storage means) in the system controller 600, and in FIG. As shown, it is transmitted from the system controller 600 to the IPU 612. Then, when reading the connected color correction chart HC, the color copying apparatus 1 displays on the liquid crystal screen 511 a screen indicating that reading is in progress as shown in FIG.

  When the IPU 612 receives the reading value and the reading reference value of the connected color correction chart HC, the IPU 612 calculates the image processing parameter as shown in S7 in FIG. 23, and the calculation result parameter as shown in S8 in FIG. To the system controller 600.

  As shown by S9 in FIG. 23, the system controller 600 stores the received parameters in the nonvolatile RAM.

  Next, a method for creating the scanner γ conversion table from the read values of the achromatic color patches in the connected color correction chart HC (see FIG. 22) in S7 of the sequence diagram of FIG. 23 will be described based on the quaternary chart shown in FIG. .

  In the quaternary chart of FIG. 27, the first quadrant (I) represents the scanner γ conversion table to be obtained, the horizontal axis represents the input value to the scanner γ conversion table, and the vertical axis represents the output after the scanner γ conversion. ing. The vertical axis of the fourth quadrant (IV) represents the read value of the achromatic color patch, and the graph represents the target value (reference value) for obtaining the scanner γ conversion table from the read value of the achromatic color patch. The horizontal axis of the third quadrant (III) is the reference value of the reading value of the achromatic color patch, and the graph represents the reading result obtained by reading the achromatic gray scale patch by the scanner unit 300. The second quadrant (II) is no conversion (through).

  According to the characteristics shown in the quaternary chart of FIG. 27, the scanner γ conversion tables of b and b ′ of the first quadrant are created from the results a and a ′ of the read values of the third quadrant.

  The target value of the read value shown in the fourth quadrant of the quaternary chart in FIG. 27 may be a different target value for each of the RGB components of the scanner γ conversion table used at the time of document copy, or the same target value. It may be a value.

  As described above, the scanner γ conversion table for correcting the machine difference of the scanner unit 300 is created.

  FIG. 28 is a flowchart schematically showing the flow of the scanner calibration process. In the scanner calibration process, the connected color correction chart HC shown in FIG. 22 is read, and the determination criterion parameter Fx ′ of the hue region and the masking coefficient are calculated based on the read result.

  First, when the operation unit 500 instructs to start reading the connected color correction chart HC, the connected color correction chart HC (see FIG. 22) is read (step S601: chart reading means), and the connected color correction chart HC is read. It is determined whether or not the read value is within a predetermined range (step S602).

  If the read value is not within the predetermined range (N in step S602), it is assumed that a document other than the connected color correction chart HC is placed on the scanner unit 300, and the current value is used as the linear masking coefficient. T (Step S603), the process ends.

  On the other hand, if the read value is within the predetermined range (Y in step S602), a scanner γ conversion table is created (step S604). As described above, the scanner γ conversion table is created using the achromatic patch portion of the connected color correction chart HC. Thereby, the machine difference of the scanner unit 300 is reduced.

Next, the read value is converted by the scanner γ conversion table and further inverted (step S605). That is, the scanner γ conversion f (S [I]) is performed on the RGB component read value S [I] of the I-th patch having 10-bit accuracy, and gradation inversion is further performed. If the gradation-inverted value S ′ [I] is assumed,
S ′ [I] = S [White] −f (S [I])
It becomes. Here, S [I] is composed of three components of Red, Green, and Blue, and S [White] is a reference value of white RGB. This is because the scanner γ conversion is performed to improve color reproducibility, and by making the color value with high saturation large and the value with low saturation small, the color can be handled easily.

  Next, the hue angle is calculated (step S606). Read values of each patch of the connected color correction chart HC Read from RGB data (Dr, Dg, Db) (= Ri, Gi, Bi (i = number of each patch)) using Expressions 13 to 29 Parameters GR, GB, and Fx ′ for dividing the RGB image data of the document for each hue are calculated.

Next, a linear masking coefficient is calculated (step S607: RGB signal correcting means, masking coefficient calculating means). For calculating the linear masking coefficient, the linear masking coefficient for each hue is calculated from the read values Ri, Gi, Bi (i = number of each patch) of each patch using the method described above and the following expression 36. .

The method will be specifically described. A value obtained by reading a point on the boundary surface that is not on the achromatic color axis with, for example, a scanner CCD showing standard spectral characteristics is (Ri, Gi, Bi) (i = hue 1 to 4). When the same point is read by another scanner, this point is different from (Ri, Gi, Bi) (i = hue 1 to 4) due to variations in the spectral characteristics of the scanner CCD (Ri ′, Gi ′). , Bi ′) (i = hue 1 to 4). As a result, the recording values of the developing portions C, M, Y, and K are (Ci ′, Mi ′, Yi ′, Ki ′) (i = hue 1 to 4). That is, the equation 32 is changed to the following equation:
It can be expressed as here,
(R (i ′), G (i ′), B (i ′)) ≈ (R (i) + ΔR (i), G (i) + ΔG (i), B (i) + ΔB (i)) (I = hue 1 to 4)
And approximate
Get. That is, instead of using the actual read values (Ri ′, Gi ′, Bi ′), a predetermined coefficient kX (X = R, G, B) is added to the difference between the reference value of the chromatic color reference patch and the read value. Are added to a scanner vector (Ri, Gi, Bi) (i = 1, 2, 3, 4) composed of RGB components stored in advance. It should be noted that the scanner vector (Ri, Gi, Bi) (i = 1, 2, 3, 4) is the same as the reference patch obtained from the reference value and the read value of the connected color correction chart HC of the chromatic color patch. Is the coefficient kX = 1 (X = R, G, B)
It becomes.

  By the way, in the present embodiment, the combination of the current value and the reference value can be selected by the operation unit as described below in accordance with the variation factor of the scanner machine difference.

  When the scanner calibration menu is called on the liquid crystal screen 511 of the operation unit 500 shown in FIG. 4, the scanner calibration screen shown in FIG. 29 is displayed. On the scanner calibration screen of FIG. 29, a key for setting a combination of “reference value” and “current value” is displayed. When [factory set value] is selected as the reference value or the current value, as shown in FIG. 30, a factory set value that is a standard read value of the connected color correction chart HC is displayed on the liquid crystal screen 511. When [read value] is selected as the current value, the read value is displayed on the liquid crystal screen 511 as shown in FIG. The factory setting value displayed in FIG. 30 and the read value displayed in FIG. 31 can be changed. Here, the reference value selection means and the current value selection means are realized.

For example, for the scanner unit 300 in which the reference patch reading value has little variation with time, the current value is a factory setting value that is a standard reading value of the connected color correction chart HC, and the reference value is stored in the ROM. Value (fixed value). Here, as the design value (fixed value), the read value of the I-th chromatic color patch is used when the values of the coefficients (Ri), (Gi), and (Bi) of the equation 38 are determined. Further, the factory setting value is obtained as a current value using a chart composed of chromatic color patches whose colors are managed in advance. In addition, when there is a variation in the color of chromatic patches (lot difference or the like), the coefficient kX (X = R, G, B) is decreased in inverse proportion to the color difference from the design value. That is, as the color difference of the ^L * ^{a *} b components of CIE Lab color difference ^L * ^{a *} b component of the reference patches using Delta] E ^* ii adjustment of the reference patches and plant used in the design of ii-th patch,
When ΔE ^* ii ≦ 1, kX = 1 (X = R, G, B)
When 1 <E ^* ii ≦ 2, kX = 0.75 (X = R, G, B)
In the case of 2 <E ^* ii ≦ 4, kX = 0.5 (X = R, G, B)
When 4 <E ^* ii ≦ 8 kX = 0.25 (X = R, G, B)
In the case of 8 <E ^* ii kX = 0.0 (X = R, G, B)
And so on.

  In addition, for the scanner unit 300 in which the reference patch reading value has little variation with time, the reading value of the connected color correction chart HC that is read each time the current value is used instead of using the factory setting value as the current value. . As the reference value, a design value (fixed value) in the ROM is used. The coefficient kX (X = R, G, B) is obtained in the same manner as described above.

  In addition, when correction is performed using the connected color correction chart HC in which the color of the reference patch used at the time of design differs by a predetermined value or more depending on the print lot difference, the scanner calibration screen shown in FIG. 32 is used. . That is, a standard reading value of the connected color correction chart HC with different colors is set as a reference value at the time of manufacture or in the market (factory setting value), and the current value is set to each connected color. A value obtained by reading the correction chart HC is used. As the coefficient in this case, as shown in FIG. 32, a correction coefficient that is inversely proportional to the color variation (standard deviation) in the printing lot is set. That is, when the standard deviation of variation is large, the coefficient kX (X = R, G, B) is set to a value close to 0, and when the standard deviation is small, the coefficient kX (X = R, G, B). ) Is set to 1 or a value close to 1. Here, a correction coefficient setting means is realized.

  Note that the liquid crystal screen 511 of the operation unit 500 is a touch panel, and after selecting a setting value to be changed, a parameter is input using a numeric keypad and is set using an enter key.

  Further, the screens shown in FIGS. 30 to 32 are displayed on a personal computer connected via a LAN cable 1000 or a personal computer connected via a USB cable, an RS-232C cable, a Centronics cable, or the like, and these screens are displayed. It may be set online from a personal computer.

And here, the left side of Expression 32 and Expression 37 is
(Y (i), M (i), C (i), K (i))
= (Y (i '), M (i'), C (i '), K (i'))
However, hue i = 1, 2, 3, 4
APS (i−j) (P = Y, M, C, K, S = B, G, R; i, j = 1, 2, 3, 4, j = 1, 2 , 3,4) is the purpose,
Get. On both sides of Equation 39,
Is the inverse of
Is applied to both sides to obtain Equation 36.

  Finally, the read value and the linear masking coefficient are stored in a nonvolatile RAM, RAM, etc. (step S608), and the process is terminated.

  As shown in the flowchart of FIG. 33, a chromatic color reference patch is created using a fixed scanner γ conversion table stored in advance without creating the scanner γ conversion table in step S604 of the flowchart of FIG. May be converted.

  Here, FIG. 34 is a class diagram of scanner calibration. FIG. 34 shows color correction coefficients (register values set in the color correction circuit (ASIC)) 801 and linear masking coefficient 803, hue determination parameter 802, scanner vector 804, scanner vector inverse matrix parameter 805, and printer vector 806 used at the time of copying. , Image density selection 807 (in the operation unit), calibration data selection I / F 808 (in the operation unit), read value (current value) 809 of the connected color correction chart HC in the object, and connected color correction in the object A chart HC reading value (current value) 810, a ROM 811 and NV-RAM (nonvolatile RAM) 812, an object connected color correction chart HC reading value (previous value) 813, and a scanner 814 are shown.

  The meaning of the figure is that the color correction coefficient 801 can be calculated from the hue determination parameter 802 and the linear masking coefficient 803, and the hue determination parameter 802 can be calculated from the scanner vector 804. The linear masking coefficient 803 is calculated from the scanner vector inverse matrix parameter 805 and the printer vector 806. The scanner vector inverse matrix parameter 805 is calculated from the scanner vector 804. The printer vector 806 is selected by image quality mode and density selection by an image selection I / F 807 on the operation unit. Printer vector 806 data is stored in the RAM 811. The scanner vector 804 is obtained from the read value (current value) 809 of the connected color correction chart HC as an object. The connected color correction chart HC read last time and stored in the NV-RAM 812 as the read value (current value) 809 of the connected color correction chart HC by the calibration data selection I / F 808 (in the operation unit). Can be selected from the read value (previous value) 813 and the read value (current value) 810 of the connected color correction chart HC newly read from the scanner 814. The read value (current value) 809 of the connected color correction chart HC and the read value (previous value) 813 of the connected color correction chart HC are stored in the NV-RAM 812.

  When the read value (previous value) 813 of the connected color correction chart HC is to be used as the read value (current value) 809 of the connected color correction chart HC, the “original value” of the scanner calibration in FIG. Select the “Return to” soft key. As a result, the value read and stored last time is called, and the color correction coefficient 801 is recalculated.

  Next, ACC (automatic gradation correction) will be described. Note that the scanner γ conversion table used in ACC (automatic gradation correction) is different from the above-described scanner γ conversion table for copying (document reading), and the spectral reflectance characteristics of the toner on the transfer paper to be read. The scanner γ conversion table for reading the ACC pattern is created using the read values of the chromatic color patches in the connected color correction chart HC so as to correct the influence of the spectral sensitivity variation of the CCD 312. .

  Then, as described later, a scanner γ conversion table for reading an ACC pattern (see FIG. 43) is created from a chromatic color patch and an achromatic color patch having different colors, and a yellow toner reading scanner γ. A method of creating a correction table (scanner γ conversion table) will be described as an example with reference to FIG.

  A chromatic color patch used for correcting yellow toner is as shown in FIG. 35, for example, and this chromatic color patch is extracted for correcting yellow toner. It is an example of the numerical value which read the color patch with the scanner used as a reference | standard. When reading yellow toner, the blue signal is used because the sensitivity of the blue signal is high. Also, different blue signals are output from a plurality of chromatic color patches having different colors. White, 2. Yellow (Yellow), 5. Blue, 6. Cyan, 10. Gray, 11. A correction table for reading yellow toner is created by using a blue signal among black RGB read signals.

  When the correction table for yellow reading at the time of executing ACC is created, since the connected color correction chart HC is created with printing ink, a deviation from the spectral reflectance of the toner occurs. Shows an example of the correction coefficient for Blue.

  The correction coefficient can be obtained based on FIG. 36 showing the relationship between the spectral sensitivity of the CCD 312 for the blue signal and the spectral reflectance of yellow toner in terms of the wavelength λ. The horizontal axis of FIG. 36 is the wavelength λ, and the vertical axis is the spectral sensitivity [%] of the CCD 312 shown on the left axis for the graph (a), and the right side for the graphs (c) and (d). This is the spectral reflectance [%] of the toner indicated on the axis. In FIG. 36, (a) is the spectral sensitivity of the blue signal filter, (c) is the spectral reflectance of yellow toner, and (d) is the spectral reflectance of yellow ink. , (D) show the spectral reflectance of the black (Bk) toner when the adhesion amount is small. For the spectral sensitivity of (a), the product of the spectral energy of the light source (halogen lamp 302) is used for the spectral transmittance of the blue filter of the CCD 312.

As can be seen from FIG. 36, the output B (CCD 312, color material) of the blue signal is the spectral sensitivity S (CCD, λ) of the CCD 312 and the spectral reflectance ρ (color material) of the color material with respect to the wavelength λ. , Λ, area ratio) is an integral value for wavelength λ with respect to the product S (CCD, λ) × ρ (color material, λ, area ratio). That is, it is given by the following equation 42.

Blue signals corresponding to the spectral sensitivity characteristic a of the CCD 312 when reading yellow toner (hereinafter abbreviated as Y toner) and yellow ink (hereinafter abbreviated as Y ink) are respectively expressed by the following equations 43, It represents like 44.
Here, the spectral sensitivity S (a, λ) is a representative value of the scanner unit 300, and the Y toner ρ (Y toner, λ) and the spectral reflectance ρ (Y ink, λ) of the Y ink are spectroscopically measured. Obtained by measuring with a colorimeter. Thus, B (a, Y toner) and B (a, Y ink) can be obtained.

From the reading value B (Y ink) of the blue signal obtained by reading the yellow patch of the printing ink on the connection color correction chart HC, Y for the reading value of Y toner at the time of ACC execution is used. When predicting the read value B (Y toner) when the toner is read, the following equation 45 is used as a coefficient k (Yellow) to be corrected.
B (Y toner) = k (Yellow) × B (Y ink) (45)
However, k (Yellow) = B (a, Y toner, 100%) / B (a, Y ink, 100%).

In the above description, the yellow toner is described. However, for other color patches, the spectral reflectance and calculation of the yellow toner are calculated in a region where the blue spectral sensitivity of the CCD 312 is not zero. The Y toner area ratio or the toner adhesion amount per unit area [mg / cm ² ]), which has substantially the same color patch reflectivity as the printing ink to be used, is used.

  For example, the spectral reflectance characteristics (i) of the blue-green ink shown in FIG. 37, the spectral reflectance (c) of the yellow toner with an area ratio of 50%, and the read value of the blue signal are yellow (Yellow). ) For a patch (Black, Green, etc.) that obtains a reading value lower than the reading value of toner (ink), the coefficient is set to 1 without calculating the correction coefficient. The correction coefficient k obtained in this way can be shown as shown in FIG.

  Next, a method of creating a conversion table for ACC pattern reading value correction will be described based on a quaternary chart of the ACC pattern reading value correction table shown in FIG.

  The first quadrant (I) in FIG. 38 represents a conversion table for ACC pattern reading value correction to be obtained. The horizontal axis represents the CCD pattern reading value and the vertical axis represents the value after conversion. The vertical axis of the fourth quadrant (IV) represents the read values after correction with the correction coefficient k of the chromatic and achromatic patches, and the graph shows the ACC pattern from the read values of the chromatic and achromatic patches. It represents a target value (reference value) for obtaining a conversion table for reading value correction. The horizontal axis of the third quadrant (III) is the reference value of the read values of the chromatic and achromatic patches, and the graph corrects the read values obtained by reading the chromatic and achromatic patches with the correction coefficient k. Value. The second quadrant (II) is no conversion (through).

  Then, conversion for correcting the ACC pattern reading value obtained from b and b ′ of the first quadrant (I) from the reading values a and a ′ of the third quadrant (III) by the characteristics shown in FIG. A table (correction table) D [ii] (ii = 0, 1, 2,..., 255) is created.

  The target value of the read value shown in the fourth quadrant (IV) of FIG. 38 is created for each toner of YMCK read by the ACC pattern. In this way, ACC (automatic gradation correction) adjustment accuracy can be improved.

  FIG. 39 shows an example of numerical values obtained by reading a color patch extracted for correcting cyan toner with a reference scanner. When reading cyan toner, the red signal is used because the sensitivity of the red signal is high. Therefore, different red signal values are output from a plurality of chromatic color patches having different colors. White, 2. 2. Yellow (Yellow) Red (or 4. Magenta); Colors between Magenta and Blue 1,6. 6. Color between Magenta and Blue Blue, 8 Cyan, 10. Gray, 11. A correction table for reading cyan toner at the time of executing ACC is created by using the chromatic color of black and the red signal of the achromatic patch.

  In this way, it is possible to prevent variations in the read image signal based on the mechanical difference of the scanner unit 300, and it is possible to improve the adjustment accuracy of automatic gradation correction (ACC), thereby further improving the image quality. be able to.

  Further, a gradation conversion table set in the image processing printer γ conversion circuit 713 at the time of gradation pattern reading is used as an image signal obtained by reading a plurality of different color patches of the connected color correction chart HC with the scanner unit 300. Since it is generated using a common one-component image signal, a scanner unit 300 corresponding to a complementary color signal of YMC toner among RGB image signals obtained by reading different color patches of the connected color correction chart HC. By generating the gradation conversion table using the read image signal, it is possible to improve the adjustment accuracy of the gradation conversion table, and it is possible to improve the image quality even in the case of linked output.

  Further, when creating the scanner γ conversion table for Cyan reading at the time of ACC execution, the connected color correction chart HC is created with printing ink, so that a deviation from the spectral reflectance of the toner occurs. Therefore, FIG. 39 shows an example of the correction coefficient for red.

  In this way, the difference between the spectral reflectance characteristic of the printing ink in the connected color correction chart HC and the spectral reflectance characteristic of the toner of the printer unit 100 that records and outputs the gradation pattern is corrected, so that it is more automatic. A scanner γ conversion table, which is an image signal conversion table for gradation correction (ACC), can be created, and the image quality can be further improved.

  Next, an operation screen for selecting an ACC (automatic gradation correction) function for image density (gradation) will be described.

  When the ACC (automatic gradation correction) menu is called on the liquid crystal screen 511 of the operation unit 500 shown in FIG. 4, the automatic gradation adjustment screen shown in FIG. 40 is displayed. Alternatively, when “execute” of automatic gradation correction for use of the printer is selected, an automatic gradation correction start screen shown in FIG. 41 is displayed on the liquid crystal screen 511. In this case, when copy use is selected on the automatic gradation adjustment screen of FIG. 40, a gradation correction table to be used when copy is used is prepared. A gradation correction table is prepared based on the reference data.

  In the automatic gradation adjustment screen of FIG. 40, if the result of image formation using the changed YMCK gradation correction table is not desirable, the pre-processing YMCK gradation correction table can be selected. As shown, the “Undo” key is displayed.

  Also, in the automatic gradation adjustment screen of FIG. 40, when “Auto gradation correction setting” is selected, “background correction”, “high density portion correction”, “RGB ratio correction”, “execution” described later. The key for selecting "" or "Non-execution" is displayed. In the “Auto gradation correction setting” menu, “Auto gradation correction setting” and “Light intensity unevenness detection setting” can be selected. Note that these selections are not always necessary, and may be always “execution”.

  Then, as described above, the color copying apparatus 1 creates a scanner γ conversion table for each RGB read component used at the time of copying from an achromatic color patch. On the other hand, the color copying apparatus 1 corrects the read values of the YMCK gradation patterns obtained by reading the adjustment pattern output during the execution of ACC (automatic gradation correction) from the chromatic color patches and the achromatic color patches. Therefore, in the former process, three RGB conversion tables are used, and in the latter process, four YMCK conversion tables are used.

  Here, the operation of automatic gradation correction (ACC) of the image density (gradation property) will be described based on the flowchart shown in FIG.

  When “execution” of automatic gradation correction for copy use or printer use is selected on the automatic gradation adjustment screen shown in FIG. 40, the automatic gradation correction start screen shown in FIG. When the “print start” key is pressed on the liquid crystal screen 511 and the automatic gradation correction is started, a plurality of density gradations corresponding to each color mode of YMCK, characters, and photographs as shown in FIG. A pattern is formed on the transfer paper (transfer material) P (step S101).

  This density gradation pattern is stored and set in advance in the ROM 716 of the IPU 612, and the written values of the pattern are 16 patterns of 00h, 11h, 22h,..., EEh, FFh in hexadecimal notation. . In FIG. 43, patches for five gradations are displayed excluding the background portion, but any value can be selected from the 00h-FFh 8-bit signal. In the density gradation pattern, a toner pattern of a character mode and a photographic mode is formed. In the character mode, a dithering process such as pattern processing is not performed, and a pattern is formed with 256 gradations of one dot. Dither processing is performed.

  When the color copying apparatus 1 outputs a pattern to the transfer paper (transfer material) P, as shown in FIG. 44, on the contact glass 3 which is a document table of the transfer paper (transfer material) P on which the density gradation pattern is recorded and output. A message to urge the user to place the camera on the LCD screen 511 is displayed. When the transfer paper on which the density gradation pattern is formed is placed on the contact glass 3 in accordance with the instruction on this screen (step S102), “read start” is selected on the screen of FIG. 44 or “cancel” "Is selected (step S103). If" Cancel "is selected, the process is terminated.

  When “reading start” is selected in step S103, the color copying apparatus 1 reads the RGB data of the YMCK density pattern by the scanner unit 300 performing main scanning sub-scanning on the transfer paper on which the density gradation pattern is formed. (Step S104). At this time, the scanner unit 300 reads the data of the pattern portion of the transfer paper on which the density gradation pattern is formed and the data of the background portion of the transfer paper.

  The color copying apparatus 1 determines whether or not the data of the pattern portion of the transfer paper has been read normally (step S105). If the data has not been read normally, it is checked whether or not the data has not been read correctly for the second time (step S105). Step S106). If it is the first time, the color copying apparatus 1 displays the screen of FIG. 44 on the liquid crystal screen 511 again. When the reading is instructed, the process returns to step S104 and the same processing as above (steps S104 and S106). In step S106, if it is the second time that reading is not performed normally, the process ends.

  In step S105, when the data of the pattern portion of the transfer paper is normally read, the color copying apparatus 1 converts each reading value of the ACC pattern into the ACC pattern reading value correction table D [ii] (ii = 0). , 1, 2,..., 255) are converted and corrected for each color of YMCK (step S107), and the background correction using the background data based on the selection result on the automatic gradation adjustment screen of FIG. It is determined whether the process is “executed” / “not executed” (step S108).

  If “execution” of the background correction process using the background data is selected in step S108, the color copying apparatus 1 performs the background data correction process for the read data (step S109), and the reference data is high. Whether the image density portion correction is “executed” / “not executed” is determined based on the selection result on the automatic gradation adjustment screen of FIG. 40 (step S110).

  If “execution” of the correction of the high image density portion of the reference data is selected in step S110, the color copying apparatus 1 performs a correction process of the high image density portion on the reference data (step S111), and YMCK gradation A correction table is created and selected (step S112). If the reference data is not corrected in step S110, the color copying apparatus 1 creates and selects the YMCK tone correction table without correcting the reference data (step S112).

  When the YMCK tone correction table is created and selected, the color copying apparatus 1 checks whether the above processing has been executed for each color of YMCK (step S113). If the above processing has not been executed for each color of YMCK, step S105 is performed. Returning to the above, the above processing is executed for each color of YMCK (steps S105 to S113).

  When the above processing is performed for each color of YMCK in step S113, the color copying apparatus 1 checks whether the above processing has been completed for each image quality mode for photographs and characters (step S114). Returning to, processing is performed in the same manner as described above (steps S105 to S114). When the processing is completed for each picture quality mode of a photograph and characters in step S114, the processing is terminated.

  During the above processing, the color copying apparatus 1 displays a screen indicating that automatic gradation correction is being performed on the liquid crystal screen 511 as shown in FIG. 45, and also displays the YMCK gradation correction table after the processing is completed. If the result of image formation is not desirable, a “Restore” key is displayed on the automatic gradation adjustment screen of FIG. 40 so that the YMCK gradation correction table before processing can be selected. .

  Next, the background correction process will be described. There are two purposes for the background correction processing, and one is to correct the whiteness of the transfer paper used during ACC. This is because the background correction processing has different values read by the scanner unit 300 depending on the whiteness of the transfer paper to be used even if images are formed on the same machine at the same time. As a demerit when the correction is not performed, for example, when recycled paper or the like having low whiteness is used for ACC, since the recycled paper generally has a lot of yellow components, a yellow gradation correction table is created. When correction is made so that the yellow component is reduced, but in this state, when copying is performed using art paper or the like with high whiteness, an image with less yellow component is obtained and the desired color reproduction cannot be obtained. Is that there is.

  Another reason for the background correction processing is that when the thickness of the transfer paper (paper thickness) used at the time of ACC is thin, the color of a pressure plate or the like that presses the transfer paper is seen through and read by the scanner unit 300. For example, when the ADF 400 is installed instead of the pressure plate, a belt 402 is used for transporting the original G. The transport belt 402 has low whiteness due to the rubber-based material used. However, since there is a slight gray color, the read image signal is also read as an image signal that is apparently high, and is created so as to be thinner when the YMCK tone correction table is created. In this state, when a transfer sheet having a large paper thickness and poor transparency is used for ACC, an image having a low overall density is reproduced, so that a desirable image is not necessarily obtained.

  In order to prevent the above-described problems, the read image signal of the pattern portion is corrected from the read image signal of the paper background portion based on the image signal of the paper background portion.

  However, there is an advantage even when the above correction is not performed, and when using a transfer paper with a lot of yellow components, such as recycled paper, the color without yellow correction is not suitable for colors containing yellow components. The reproduction may be improved. In addition, when only the transfer paper having a thin paper thickness is always used, there is an advantage that the gradation correction table is created in a state matched to the thin paper.

  Therefore, the color copying apparatus 1 can turn on / off the correction of the background portion according to the usage status of the color copying apparatus 1 and the user's preference by the key operation of the operation unit 500. it can.

  Next, the operation and processing for automatic gradation correction will be described. A read value obtained by reading the pattern in which the writing value LD [i] (i = 0, 1,..., 9) of the gradation pattern (see FIG. 43) formed on the transfer paper is read by the scanner unit 300 is obtained. V [t] [i] ≡ (r [t] [i], g [t] [i], b [t] [i]) (t = Y, M, C, or, K, i = 0, 1, ..., 9).

Instead of (r, g, b), brightness, saturation, hue angle (L ^* , c ^* , h ^* ), or brightness, redness, blueness (L ^* , a ^* , b ^* ), etc. May be represented.

  The reference white reading value stored in advance in the ROM 716 or the RAM 717 is set to (r [W], g [W], b [W]).

  Next, a method of generating a gradation conversion table (LUT) performed by the image processing printer γ conversion circuit 713 when ACC is executed will be described.

  In the gradation pattern read value v [t] [i] ≡ (r [t] [i], g [t] [i], b [t] [i]), the image signal of each complementary color of YMC toner. Are b [t] [i], g [t] [i], and r [t] [i], respectively, so that only the complementary color image signals are used. Here, for simplicity of description, a [t] [i] (i = 0, 1, 2,..., 9; t = C, M, Y, or, K) is used. Processing is simple if a gradation conversion table is created.

  For black toner, sufficient accuracy can be obtained by using any of RGB image signals, but here, a G (green) component is used.

  The reference data includes the reading value v0 [t] [i] ≡ (r0 [t] [i], g0 [t] [i], b0 [t] [i]) of the scanner unit 300 and the corresponding laser writing value. It is given by a set of LD [i] (i = 1, 2,..., M). Similarly, in order to simplify the description using only YMC complementary color image signals, A [t] [n [i]] (0 ≦ n [i] ≦ 255; i = 1, 2,... , M; t = Y, M, C, or, K). m is the number of reference data.

  The YMCK gradation conversion table is obtained by comparing the a [LD] with the reference data A [n] stored in the ROM 716.

  Here, n is an input value to the YMCK gradation conversion table, and the reference data A [n] is the YMC toner output with the laser writing value LD [i] after the input value n is YMCK gradation converted. This is the target value of the read image signal obtained by reading the pattern with the scanner unit 300. Here, the reference data includes two types of values: a reference value A [n] that is corrected according to the image density that can be output by the printer, and a reference value A [n] that is not corrected. The color copying apparatus 1 determines whether to perform correction based on determination data stored in advance in the ROM 716 or the RAM 717.

  The color copying apparatus 1 obtains the laser output value LD [n] corresponding to the input value n to the YMCK gradation conversion table by obtaining the LD corresponding to A [n] from the a [LD]. .

  By obtaining this laser output value LD [n] with respect to the input values i = 0, 1,..., 255 (in the case of an 8-bit signal), a gradation conversion table can be obtained.

  In this case, instead of performing the above processing on all values for the input values n = 00h, 01h,..., FFh (166 base number) for the YMCK gradation conversion table, ni = 0, 11h, 22h,. .. The above processing is performed for the jump value such as FFh, and other points are interpolated with a spline function or the like, or among the YMCKγ correction tables stored in the ROM 716 in advance, the above The closest table that passes through the set of (0, LD [0]), (11h, LD [11h]), (22h, LD [22h]), ..., (FFh, LD [FFh]) Select.

  The above process will be described with reference to FIG. In the first quadrant (a) of FIG. 46, the horizontal axis is the input value n to the YMCK gradation conversion table, and the vertical axis is the reading value (after processing) of the scanner unit 300, see above. Data A [i] is represented. The reading values (after processing) of the scanner unit 300 are RGBγ conversion (no conversion is performed here) with respect to the value obtained by reading the gradation pattern with the scanner unit 300, and several reading data in the gradation pattern. It is a value after the averaging process and the addition process, and is processed here as a 12-bit data signal in order to improve calculation accuracy.

  In the second quadrant (b) of FIG. 46, the horizontal axis represents the read value (after processing) of the scanner unit 300, similarly to the vertical axis.

  In the third quadrant (c) of FIG. 46, the vertical axis represents the writing value of the laser beam (LD). The data a [LD], which is the laser beam writing value, represents the characteristics of the printer unit 100, and the writing value of the laser beam (LD) of the pattern actually formed is 00h (background), 11h. , 22h,..., EEh, FFh are 16 points and show skipped values. Here, the detected points are interpolated and treated as a continuous graph.

  The graph (d) of the fourth quadrant in FIG. 46 is the YMCK gradation conversion table LD [i], and the purpose is to obtain this YMCK gradation conversion table.

  The vertical axis and horizontal axis of the graph (f) are the same as the vertical axis and horizontal axis of the graph (d). When forming a gradation pattern for detection, the YMCK gradation conversion table (g) shown in the graph (f) is used.

  The horizontal axis of the graph (e) is the same as that of the third quadrant (c), and the writing value of the laser beam (LD) at the time of gradation pattern creation and the reading value of the gradation pattern scanner unit 300 (after processing) ) For the sake of convenience for expressing the relationship with ().

  In FIG. 46, reference data A [n] is obtained for a certain input value n, and a laser beam (LD) output LD [n] for obtaining A [n] is used as a gradation pattern read value a [LD]. Is obtained along the arrow (l) in the figure.

  FIG. 47 is an example of a Green data conversion table. In the reading value, the portion with a large amount of reflected light from the 1000H side document (bright) uses the reading value of the reading value of calibration pattern 1 of Magenta, and the portion with a small amount of reflected light from the 0H side document (dark) is black. Generated using the reading of.

  Next, the calculation procedure of ACC will be described based on the flowchart of FIG. In FIG. 48, in the gradation conversion table creation process at the time of ACC, first, the color copying apparatus 1 has input values necessary for obtaining a YMCKγ correction table (gradation conversion table), for example, n [i] = 11 ( h) × i (i = 0, 1,..., imax = 15) is determined (step S201).

  That is, the graph of the printer characteristics of the third quadrant is the same as that of the graph when RGBγ conversion is performed, but the characteristics of the RGBγ conversion table of the second quadrant are different. Accordingly, it is necessary to change the reference data of the first quadrant, but the characteristics of the final result YMCK gradation conversion table LD [n] match.

  As described above, this is dealt with by changing the reference data depending on whether or not processing is performed using the RGBγ conversion table. An example of the RGBγ conversion table used in this embodiment is shown.

  Next, the color copying apparatus 1 corrects the reference data A [n] according to the image density that can be output by the printer unit 100 (step S202).

  That is, the writing value of the laser beam for obtaining the maximum image density that can be created by the printer unit 100 is FFh (hexadecimal number display), and the read value m [FFh] of the gradation pattern at this time is mmax. Reference data A [i] (i = 0, 1,..., I1) that is not corrected from the low image density side to the intermediate image density side, and reference data A [i] (not corrected on the high image density side) , imax−1) (i1 ≦ i2, i2 ≦ imax−1) and reference data A [i] (i = i1 + 1,..., i2) to be corrected.

Hereinafter, a specific calculation method will be described on the assumption that the image signal is proportional to the document reflectance without RGB-γ conversion. From the reference data A [i2 + 1] having the lowest image density in the high image density portion and the reference data A [i1] having the lowest image density in the low image density portion among the reference data not to be corrected, The difference Δref of the data is obtained.
Δref = A [i1] −A [i2 + 1] (46)
Here, Δref> 0 in the case of reflectance linearity or lightness linear that does not perform RGBγ conversion, which is inversion processing.

On the other hand, the difference Δdet is similarly obtained by the following equation 47 from the read value mmax of the gradation pattern that can obtain the maximum image density that can be created by the printer unit 100.
Δdet = A [i1] −mmax (47)

Then, reference data A [i] (i = i1 + 1,..., I2) obtained by correcting the high density portion is obtained by the following equation 48.
A [i] = A [i1] + (A [i] −A [i1]) × (Δdet / Δref) (48)
However, i = i1 + 1, i1 + 2,..., I2-1, i2.

  Next, the color copying apparatus 1 obtains the read image signal m [i] of the scanner unit 300 corresponding to n [i] from the reference data A [n] (step S203).

  In order to obtain the read image signal m [i], actually, the reference data A [n [j]] (0 ≦ n [j] ≦ 255, j = 0) corresponding to the skipped n [j]. ,..., Jmax, n [j] ≦ n [k] forj ≦ k) are obtained as follows.

  That is, j (0 ≦ j ≦ jmax) that satisfies n [j] ≦ n [i] <n [j + 1] is obtained.

  In the case of an 8-bit image signal, the reference data is obtained as n [0] = 0, n [jmax] = 255, n [jmax + 1] = n [jmax] +1, A [jmax + 1] = A [jmax]. Calculation becomes easy.

  Further, the reference data interval n [j] is as small as possible, so that the accuracy of the finally obtained γ correction table increases.

Next, the color copying apparatus 1 corrects the ACC pattern read value a [LD] with respect to the write value LD as a correction table D [ii] (ii = 0, 1, 2,. , 255), the following correction is performed (step S204).
a1 [LD] = D [a [LD]]
This a1 [LD] is expressed as a [LD] below.

From j thus obtained, m [i] is obtained by the following equation 49.
m [i] = A [j] + (A [j + 1] -A [i]). (n [i] -n [j])
/ (N [j + 1] -n [j]) (49)

In the equation 48, the interpolation is performed by a linear equation, but the interpolation may be performed by a high-order function or a spline function. In that case, the following equation 50 is given.

When the color copying apparatus 1 obtains m [i], it obtains the writing value LD [i] of the laser beam (LD) for obtaining m [i] in the same procedure (step S205).
When processing image signal data that has not been subjected to RGBγ conversion, a [LD] decreases as the value of the laser beam (LD) increases, as shown below.
For LD [k] <LD [k + 1], a [LD [k]] ≧ a [LD [k + 1]]
Here, the values at the time of pattern formation are 10 values of LD [k] = 00h, 11h, 22h,..., 66h, 88h, AAh, FFh, (k = 0, 1,..., 9). did. This is because the change in the reading value of the scanner unit 300 with respect to the toner adhesion amount is large at an image density with a small amount of toner adhesion. This is because the change in the reading value of the scanner unit 300 with respect to the toner adhesion amount is small, so that the interval is widened for reading.

  In this way, it is possible to suppress toner consumption as compared with the case of increasing the number of patterns such as LD [k] = 00h, 11h, 22h,..., EEh, FFh (16 points in total) and the like. In the image density area, there is little change to the LD writing value, and the read value is likely to be reversed due to potential unevenness on the photosensitive drums 104K to 104C, toner adhesion unevenness, fixing unevenness, potential unevenness and the like. There is a merit that even if the interval between the LD write values is narrowed, it is not always effective in improving the accuracy. For this reason, the pattern is formed with the LD write values as described above.

Then, LD [i] is set as follows for LD [k] where a [LD [k]] ≧ m [i]> a [LD [k + 1]].
LD [i] = LD [k] + (LD [k + 1] −LD [k]) · (m [i] −a [LD [k]]) / (a [LD [k + 1]] − a [LD [ k]])

When 0 ≦ k ≦ kmax (kmax> 0) and a [LD [kmax]]> m [i] (when the image density of the target value obtained from the reference data is high), LD [ i] is predicted by extrapolating with a linear equation as follows.
LD [i] = LD [k] + (LD [kmax] −LD [kmax−1]) · (m [i] −a [LD [kmax−1]]) / (a [LD [kmax]] − a [LD [kmax-1]])

  As described above, a set (n [i], LD [i]) (i = 0, 1,..., 15) of the input value n [i] and the output value LD [i] to the YMCKγ correction table is obtained. Can do.

  As described above, extrapolation may be performed by a method such as taking a logarithm as well as extrapolating by a linear expression.

  Then, based on the obtained (n [i], LD [i]) (i = 0, 1,..., 15), interpolation is performed with a spline function or the like, or it is stored in the ROM 716. A gradation conversion table is obtained by selecting the γ correction table (step S206).

  In this embodiment, in order to correct the difference in spectral characteristics for each CCD, the above-described linear masking coefficient is used as a new linear masking based on the read value of the standard chart of the scanner data calibration shown in FIG. Calculate the coefficient. The method will be described below.

A value when a point on the boundary surface that is not on the achromatic color axis is read by, for example, a scanner CCD showing standard spectral characteristics is defined as (Ri, Gi, Bi) (i = hue 1 to 4). When the same point is read by another scanner, this point is different from (Ri, Gi, Bi) (i = hue 1 to 4) due to variations in the spectral characteristics of the scanner CCD (Ri ′, Gi ′, Bi ′) (i = hue 1 to 4). As a result, the recording values of the developing portions C, M, Y, and K are calculated as (Ci ′, Mi ′, Yi ′, Ki ′) (i = hue 1 to 4) according to (Equation 1). That is, Expression 33 can be expressed as the following Expression 55.

Since we want to make the YMCK output after the linear masking process the same, if Equation 32 = Expression 55,
From Equation 56, in order to obtain the linear masking coefficient aPS (hue 3′-4 ′) (P = Y, M, C, K; S = R, G, B) of the hue region 3′-4 ′, On both sides,
The inverse of
Over
The linear masking coefficient aPS (hue 3′-4 ′) (P = Y, M, C, K; S = R, G, B) of the hue region 3′-4 ′ can be obtained. Similarly, the linear masking coefficient aPS (each hue) (P = Y, M, C, K; S = R, G, B) can be obtained for each of the other hues.

  The printer vector P (i) in Equation 57 (P = Y, M, C, K; i = each hue) is changed in accordance with the original type of the original to be copied, so that the color reproducibility of the copy is obtained. Can be improved. Document types include, for example, a printed document using ink as a color material, a photographic paper photo document using a YMC photosensitive layer as a color material, a copy document using toner as a color material, an inkjet document using an inkjet printer output as a document, and special color ink. Examples include map manuscripts that use, color correction coefficients for fluorescent pens for identifying fluorescent pens, and the like.

In other words, the printer vector P (i) in Expression 57 (P = Y, M, C, K; i = each hue) is a P document type (i) (P = Y, M, C, K; i = each hue, document type = printing, photographic paper photograph, copy document, map, inkjet, highlighter etc) aPS document type corresponding to each image quality mode corresponding to each image quality mode selected in the operation unit (Hue) (P = Y, M, C, K; S = R, G, B, constant) is calculated and set in a circuit (ASIC) for use in copying.
And

  A method of calculating the hue region determination reference parameter Fx ′ and the masking coefficient based on the reading result by reading the scanner data / calibration chart shown in FIG. 22 will be described with reference to the flowchart of FIG. 49. FIG. 49 is a flowchart showing correction by scanner data calibration according to the present invention.

  The scanner data / calibration chart is read (S1001). As an example, the scanner data / calibration standard chart shown in FIG. 22 is placed on the document table of the scanner unit 300, and is read by the scanner unit 300.

  Next, the hue angle is calculated (S1002). Reading value of each patch of scanner data / calibration chart Reading from RGB data (Dr, Dg, Db) (= Ri, Gi, Bi (i = number of each patch)) using Expressions 13 to 29 GR, GB, and Fx ′ are calculated as parameters for dividing the RGB image data of the document for each hue.

  Next, a linear masking coefficient is calculated (S1003). A linear masking coefficient for each hue is calculated from Expression 57 and the read values Ri, Gi, Bi (i = number of each patch) of each patch.

  Finally, the reading value and the coefficient are stored (S1004).

  Subsequently, characteristic functions of the present embodiment will be described. In the present embodiment, intermediate results for obtaining image processing parameters for image processing of image data are calculated and held in stages for each predetermined operation of the image processing apparatus, and the intermediate results are obtained. Recalculation determination information for determining whether or not to recalculate is stored, recalculation of intermediate results of image processing parameters is determined based on the recalculation determination information of intermediate results, and image processing parameters are It is made to generate.

More specifically, an intermediate result (scanner vector, printer vector, scanner vector inverse matrix and linear masking coefficient shown in Expression 57) for obtaining image processing parameters is obtained during a predetermined operation as shown below. It is a thing.
1. 1. When image processing parameters are initialized or when the power is turned on. 2. When reading a reference chart (calibration chart) When correcting image data

[When initializing image processing parameters or turning on the power]
First, an intermediate result calculation process at the time of initialization of image processing parameters or power-on will be described. FIG. 50 is a flowchart showing the flow of the intermediate result calculation process when the image processing parameter is initialized or when the power is turned on.

  As shown in FIG. 50, first, [mechanical difference correction value 1-1] in the entire hue (for each hue such as black, white and RGBYMC) area is read from the nonvolatile RAM (step S1001) to obtain a linear masking coefficient. [Scanner vector] is calculated and held (step S1002). If no correction value is set, the correction amount is treated as zero.

  In the subsequent step S1003, [image processing condition 1-1] is assumed. This [image processing condition 1-1] is information used to obtain [scanner vector]. For example, the setting is expected to be most used in the full-color copying apparatus 1, no inversion (positive image), no color conversion is performed, the conversion width at the time of color conversion is a default, and based on the color material used Assume that the original type is a printed original.

  Thereafter, the [scanner vector inverse matrix] of the entire hue (each hue such as RGBYMC except black and white) area is calculated and held (step S1004).

  Also, as shown in FIG. 50, [mechanical difference correction value 1-2] in the entire hue (excluding black and white, each hue such as RGBYMC) area is read from the nonvolatile RAM (step S1005), and [Image Processing Condition] 1-2] is assumed (step S1006). This [image processing condition 1-2] is information used to obtain [printer vector]. This includes information that overlaps with [Image processing condition 1-1] described above. For example, it is assumed that the setting is expected to be used most in the full-color copying apparatus 1. For example, it is assumed that the density adjustment is a default value in a full-color character / photo: print original mode.

  In subsequent step S1007, [printer vector] is calculated and held. If no correction value is set, the correction amount is treated as zero.

  In step S1008, the product of the matrix of [scanner vector inverse matrix] calculated in step S1004 and [printer vector] calculated in step S1007 is obtained, and all hues (each hue component such as RGBYMC except black and white) are obtained. ) Calculate and hold [Hue Division Masking Coefficient] of the area.

  In addition, as shown in FIG. 50, [scanner γ node data] is read from the nonvolatile RAM (step S1009). [Scanner γ node data] includes, for example, a plurality of points for obtaining a one-dimensional table representing the input / output relationship between inputs 0 to 255 and outputs 0 to 255 by, for example, spline interpolation.

  In the subsequent step S1010, [image processing condition 1-3] is assumed and held as an initial value of information for obtaining [scanner γ table].

  Then, interpolation processing such as spline interpolation is performed on [scanner γ node data] read from the nonvolatile RAM to obtain a [scanner γ table], which is stored in the volatile RAM (S1011).

[When reading the reference chart (calibration chart)]
Next, an intermediate result calculation process at the time of reading a reference chart (calibration chart) will be described. FIG. 51 is a flowchart showing the flow of the intermediate result calculation process at the time of reading the reference chart (calibration chart).

  As shown in FIG. 51, first, it is determined whether the scanner output is stable (step S1501). As an example, this is determined by the elapsed time immediately after the power is turned on. Immediately after the power is turned on, for example, the color temperature of the image data read when reading a blank original is low, and the color temperature rises with time, and the color temperature stabilizes after a predetermined time. Because.

  If it is determined that the scanner output is not stable (No in step S1501), the user is notified that the scanner output is not determined on the liquid crystal screen 511 of the operation unit 500 or the screen of the host computer 740. Therefore, after a predetermined time elapses, is it executed again? "Is displayed (step S1502). If the user selects “execute” after the predetermined time has elapsed (Yes in step S1503), after waiting for the predetermined time (step S1504), the process returns to step S1501. If the user selects “do not execute” (No in step S1503), the process ends.

  When it is determined that the scanner output is stable (Yes in step S1501), when the reference chart (calibration chart) is read (Yes in step S1505), the read value is acquired (step S1506).

  Subsequently, [reference value 1-1] for correcting [scanner vector] is called from the nonvolatile RAM or ROM, and [mechanical difference correction value 1-1] used in the previous correction is stored in the nonvolatile RAM. (Step S1507). If no previous correction has been performed, the initial value (0) is used.

  On the other hand, [mechanical difference correction value 1-2] of all hues (black, white, RGBYMC, and other hues) for correcting [scanner vector] is read from the reference chart (calibration chart) read value and [reference value]. 1-1] (step S1508), and updates [scanner vector] for all hues (for each hue such as black, white, and RGBYMC) (step S1509).

  FIG. 52 is a flowchart showing the flow of scanner vector update processing. As shown in FIG. 52, step S1601 indicates the start of loop processing for calculating [scanner vector] for each of the image processing conditions. As an image processing condition, loop processing is performed according to whether or not “positive”, “negative”, etc. are reversed. As the image processing conditions, loop processing is performed in accordance with the type of original to be read such as “print original”, “photographic paper original”, “copy original”, “fluorescent pen”, and the like. However, with respect to the document type, it is possible to select, for example, to perform a correction process for a frequently used specific document type by selecting “Calculate / Do not” according to the setting of the operation unit 500 or the like. Note that when “do not calculate” is selected, a fixed value stored in the ROM is used.

  Step S1602 represents the beginning of a loop for obtaining the [scanner vector] of all hues (each hue such as RGBYMC, excluding black and white). For each hue, the absolute value of the difference between [mechanical difference correction value 1-1] and [mechanical difference correction value 1-2] is compared with [correction value threshold 1], and [mechanical difference correction value 1-1]. If the absolute value of the difference between the value and [machine difference correction value 1-2] is less than or equal to [threshold value 1 of correction value] (Yes in step S1603), [scanner vector] is not updated. On the other hand, when the absolute value of the difference between [mechanical difference correction value 1-1] and [mechanical difference correction value 1-2] is larger than [correction value threshold value 1] (No in step S1603), the [ [Scanner vector] is updated based on [Machine difference correction value 1-2] (step S1604). The updated [mechanical difference correction value 1-2] is stored in the nonvolatile RAM as a new [mechanical difference correction value 1-1] (step S1605). Step S1606 is the end of a loop that calculates each hue, and step S1607 is the end of a loop that calculates each image processing condition.

  If the apparatus is on standby (Yes in step S1510), [scanner vector inverse matrix] is updated (step S1511).

  FIG. 53 is a flowchart showing the flow of the scanner vector inverse matrix update process. As shown in FIG. 53, first, a calculation time is used as a reference (step S2101). Step S2102 indicates the start of loop processing for calculating [scanner vector inverse matrix] for each of the image processing conditions. As an image processing condition, loop processing is performed according to whether or not “positive”, “negative”, etc. are reversed. As the image processing conditions, loop processing is performed in accordance with the type of original to be read such as “print original”, “photographic paper original”, “copy original”, “fluorescent pen”, and the like. However, with respect to the document type, it is possible to select, for example, to perform a correction process for a frequently used specific document type by selecting “Calculate / Do not” according to the setting of the operation unit 500 or the like. Note that when “do not calculate” is selected, a fixed value stored in the ROM is used. Further, as an image processing condition, a loop process is performed according to a combination of conversion colors of a color conversion process for converting a document color (“red” as an example) into a copy color (“blue” as an example). Furthermore, as the image processing conditions, loop processing is performed according to the above-described color conversion range of the original color (for example, “narrow” or “wide” of the “red” hue range of the original). That is, step S2102 represents the beginning of a quadruple loop process.

  In the next step S2103, an update processing routine of [scanner vector inverse matrix] under a predetermined condition is called. FIG. 54 is a flowchart showing the flow of the scanner vector inverse matrix update process under a predetermined condition. As shown in FIG. 54, first, it is determined whether or not the image processing condition to be calculated is satisfied (step S2201).

  If it is not the image processing condition to be calculated (No in step S2201), the fixed value stored in the ROM is used (step S2202).

  If the image processing conditions are to be calculated (Yes in step S2201), the process proceeds to step S2203. Step S2203 represents the beginning of a loop for obtaining [scanner vector inverse matrix] of all hues (each hue such as RGBYMC, excluding black and white).

  In the subsequent step S2204, it is determined whether or not a condition for calculating [scanner vector inverse matrix] of a predetermined hue is satisfied. As shown in Expression 57, this is determined to be a condition for calculation when the adjacent hue and the scanner vector of the hue of black or white change.

  If it is determined that the conditions for calculating the [scanner vector inverse matrix] for a predetermined hue are satisfied (Yes in step S2204), a process for obtaining the [scanner vector inverse matrix] for each hue from [scanner vector] is performed (step S2205). . Step S2206 is the end of a loop for calculating each hue.

  Returning to FIG. 53, the integrated time of the processing time required for the calculation is obtained (step S2104), it is determined whether it is within the time limit, and if the time limit is exceeded (No in step S2105), the calculated image processing is performed. The conditions are stored (step S2109) and the process ends.

  On the other hand, if it is within the time limit (Yes in step S2105), the used memory amount used to store the intermediate result (here, [scanner vector inverse matrix]) is accumulated (step S2106), and the accumulated memory is accumulated. It is determined whether or not the value is in the allowable memory (step S2107). Whether or not the memory is allowable is actually determined by whether or not there is a space for storing an intermediate result ([scanner vector inverse matrix]) calculated under the following different image processing conditions.

  If the integrated value of the used memory is within the allowable memory (Yes in step S2107), the process proceeds to step S2108. In step S2108, calculation is performed under the next image processing condition as the end of the image processing condition loop.

  On the other hand, if an allowable memory over is predicted (No in step S2107), the process is terminated, and the above-described step S2109 is executed.

  Returning to FIG. 51, in step S1512, [reference value 2-1] for correcting [printer vector] is called from the data in the nonvolatile RAM or ROM and [machine difference correction value 2] used in the previous correction is used. -1] is called from the nonvolatile RAM. If no previous correction has been performed, the initial value (0) is used.

  In subsequent step S1513, [mechanical difference correction value 2-2] for all hues (black, white, RGBYMC, and other hues) for correcting [printer vector] is used as a reference chart (calibration chart) read value. [Reference value 2-1] is calculated (step S1513), and [printer vector] is updated (step S1514).

  FIG. 55 is a flowchart showing the flow of printer vector update processing. As shown in FIG. 55, step S1701 indicates the start of loop processing for calculating [printer vector] for each of the image processing conditions. As image processing conditions, loop processing is performed according to image density adjustment, color balance adjustment, and the like. Since [Printer vector] has a relatively simple calculation time and many processing conditions, some typical conditions are calculated, or only the default conditions are calculated.

  Step S1702 represents the beginning of a loop for obtaining [printer vector] of all hues (each hue such as RGBYMC, excluding black and white). For each hue, the absolute value of the difference between [mechanical difference correction value 2-1] and [mechanical difference correction value 2-2] is compared with [threshold value 2 of correction value], and [mechanical difference correction value 2-1]. And [machine difference correction value 2-2] are less than [correction value threshold 2] (Yes in step S1703), [printer vector] is not updated. When the difference between [mechanical difference correction value 2-1] and [mechanical difference correction value 2-2] is larger than [correction value threshold 1] (No in step S1703), the [printer vector] of each hue is set to [ [Printer vector] is updated based on the machine difference correction value 2-2] (step S1704). Then, the updated [machine difference correction value 2-2] is stored in the nonvolatile RAM as a new [machine difference correction value 2-1] (step S1705). Step S1706 is the end of a loop that calculates each hue, and step S1707 is the end of a loop that calculates each image processing condition.

  In addition, the [reference value 3-1] for correcting the [scanner γ table] is called from the data in the nonvolatile RAM or ROM, and the [machine difference correction value 3-1] used in the previous correction is Called from the data in the nonvolatile RAM or ROM (step S1515), [mechanical difference correction value 3-2] for correcting [scanner γ table] is calculated (step S1516).

  Next, when the difference between the absolute values of [mechanical difference correction value 3-1] and [mechanical difference correction value 3-2] is equal to or smaller than [correction value threshold 3] (No in step S1517), [mechanical difference] The correction value 3-2] is stored in the nonvolatile RAM as a new [mechanical difference correction value 3-1] (step S1518), and the [scanner γ table] is updated (step S1519).

  FIG. 56 is a flowchart showing the flow of the scanner γ table update process. Step S1801 indicates the beginning of a loop process for calculating [printer vector] for each of the image processing conditions. As the image processing condition, loop processing is performed according to the image quality mode. As the image quality mode, only typical settings such as default (print document mode) are calculated.

  In step S1802, [scanner γ node data] is calculated. The algorithm to be calculated generates nodes for spline interpolation in the same manner as ACC (automatic gradation correction) in the printer γ table.

  In step S1803, [scanner γ node data] composed of a plurality of points calculated in step S1802 is stored in the nonvolatile RAM.

  Then, [scanner γ node data] is spline-interpolated (as an example) to generate a [scanner γ table] and hold it in the volatile RAM (step S1804).

  Step S1805 is the end of a loop that calculates each image processing condition.

[When correcting image data]
The intermediate result (scanner vector, printer vector, scanner vector inverse matrix, linear masking coefficient) is calculated and held by the above processing. Such intermediate results can be updated.

  FIG. 57 is a flowchart showing the flow of image data correction processing. As shown in FIG. 57, first, the user directly sets the image processing conditions in the operation unit 500, or inputs the image processing conditions online to the color copying apparatus 1 from a host computer 740 on the network (step). S2301). For example, [Image processing condition 1] shown in FIG. 57 is a condition for determining the update condition of the scanner vector inverse matrix, [Image processing condition 2] is a condition for updating the printer vector, and [Image processing condition 3] is This is a condition for determining whether to update the scanner γ table.

  Thereafter, when the user instructs the color copying apparatus 1 to start reading or image processing from the operation unit 500 or the host computer 740 on the network (step S2302), image processing parameters are calculated (step S2303). Then, image processing is executed (step S2304).

  FIG. 58 is a flowchart showing the flow of the image processing parameter calculation process. As shown in FIG. 58, first, [image processing condition 1], [image processing condition 2], and [image processing condition 3] set in step S2301 are acquired (step S2401).

  First, [Image processing condition 1] will be described. When [Image processing condition 1] is acquired and held (step S2402), it is determined whether or not [scanner vector] has been updated based on whether or not step S1604 (see FIG. 52) described above has been executed (step S2402). S2403). For example, if step S1604 has not been executed, it is determined that [scanner vector] has not been updated. It is also possible to calculate [scanner vector] under [image processing condition 1], compare the stored [scanner vector], and determine that the scanner vector has not been updated if there is no difference. is there. If the image processing condition stored in step S2109 is different, it can be determined that the scanner vector has been updated.

  If it is determined that [scanner vector] has not been updated (No in step S2403), [image processing condition 1] changes from [image processing condition 1-1] in which [scanner vector inverse matrix] is calculated. It is determined whether or not there is (step S2404).

  If it is determined that [Image processing condition 1] has changed (Yes in step S2404), or if it is determined that [scanner vector] has been updated (Yes in step S2403), the [scanner vector of predetermined condition] Inverse matrix] is updated and held (step S2405).

  Next, [Image processing condition 2] will be described. When [Image processing condition 2] is acquired and held (step S2406), it is determined whether or not [printer vector] has been updated based on whether or not step S1703 (see FIG. 55) described above has been executed (step S2406). S2407). For example, if step S1703 has not been executed, it is determined that [printer vector] has not been updated.

  If it is determined that [printer vector] has not been updated (No in step S2407), it is determined whether [image processing condition 2] has changed from [image processing condition 1-2] (step S2408). ).

  If it is determined that [Image processing condition 2] has changed (Yes in step S2408), or if it is determined that [Printer vector] has been updated (Yes in step S2407), then [Printer vector of predetermined condition] ] Is updated and held (step S2409).

  In step S2410, a [linear masking coefficient] is calculated from the [scanner vector inverse matrix] updated / held in step S2405 and the [printer vector] updated / held in step S2409.

  Next, [Image processing condition 3] will be described. When [Image processing condition 3] is acquired and held (step S2411), it is determined whether [Image processing condition 3] has changed (step S2412). If [Image processing condition 3] has changed from [Image processing condition 1-3] or is different from the update condition of [Scanner γ table] in step S1519, [Image processing condition 3] is Judge that it has changed.

  If it is determined that [Image processing condition 3] has changed (Yes in step S2412), [Scanner γ table] is updated and held (step S2413).

  As described above, according to the present embodiment, the intermediate calculation result for obtaining the image processing parameter is calculated step by step for each predetermined operation when the optimum image processing parameter with the scanner machine difference corrected is applied. And storing recalculation determination information for determining whether to recalculate the intermediate calculation result, determining recalculation of the intermediate calculation result based on the recalculation determination information, and generating an image processing parameter, Since the time required for calculation can be minimized by minimizing the number of calculations, it is possible to broaden the user's setting conditions for applying correction for scanner differences, and as a result, scanned image data and printed matter A preferable color reproducibility can be obtained.

  When there are a plurality of scanner units 300, the above-described “intermediate result calculation process when initializing image processing parameters or turning on the power” and “intermediate result calculation when reading a reference chart (calibration chart)” are described. The “processing” and “image data correction processing” may be executed for each of the plurality of scanner units 300. By storing the intermediate calculation results for each of the image reading units in this way, the calculation time can be reduced even when a plurality of image reading units are provided.

1 is a system configuration diagram when a color copying apparatus to which an image processing apparatus according to an embodiment of the present invention is applied is connected. 1 is a front view of a schematic configuration of a main part of an electrophotographic color copying apparatus. FIG. 3 is an enlarged front view of a scanner unit and an ADF portion of the color copying apparatus of FIG. 2. FIG. 3 is a top view of the color copying apparatus of FIG. 2. FIG. 3 is a front view of a main part schematic configuration showing a control system of the color copying apparatus of FIG. 2. FIG. 3 is a circuit block configuration diagram centering on an IPU and a printer unit of the color copying apparatus of FIG. 2. FIG. 7 is a detailed circuit block diagram of the MTF in FIG. 6. It is a figure which shows an example of the Laplacian filter of FIG. FIG. 8 is a diagram illustrating a sub-scanning direction edge detection filter as an example of the edge amount detection filter of FIG. 7. It is a figure which shows the main scanning direction edge detection filter as an example of the edge amount detection filter of FIG. It is a figure which shows the diagonal direction detection filter as an example of the edge amount detection filter of FIG. It is a figure which shows another diagonal direction detection filter as an example of the edge amount detection filter of FIG. It is a figure which shows an example in which the edge degree was table-converted by the table conversion circuit. It is a figure of the color space for demonstrating a color correction process. It is a figure of the color space for demonstrating a color correction process. It is a figure of the color space for demonstrating a color correction process. It is a figure of the color plane for demonstrating a color correction process. It is a flowchart which shows the flow of a hue determination process. It is a figure of the color plane for demonstrating a color correction process. It is a conceptual diagram of the area process of the area process part of FIG. FIG. 3 is a block diagram of a laser modulation circuit of a printer unit of the color copying apparatus of FIG. 2. FIG. 3 is a circuit block configuration diagram of a scanner unit in FIG. 2. FIG. 20 is a conceptual diagram of white correction and black correction by the shading correction circuit of FIG. 19. It is explanatory drawing of the sample hold process of the read signal by the S / H circuit of FIG. It is a top view which shows an example of the chart for connection color correction | amendment used by scanner calibration. FIG. 3 is a sequence diagram showing an execution procedure of scanner calibration by the color copying apparatus of FIG. 2. It is a figure which shows the liquid crystal screen which displays various adjustment screens. It is a figure which shows the liquid crystal screen which displays a scanner calibration start screen. It is a figure which shows the liquid crystal screen which displays the reading screen of the chart for connection color correction | amendment in scanner calibration mode. It is a figure which shows the quaternary chart in scanner calibration. It is a flowchart which shows the flow of a scanner calibration process roughly. It is a figure which shows the liquid crystal screen which displays a scanner calibration screen. It is a figure which shows the liquid crystal screen which displays a factory adjustment value. It is a figure which shows the liquid crystal screen which displays a reading value. It is a figure which shows the liquid crystal screen which displays a correction coefficient. It is a flowchart which shows the flow of a scanner calibration process roughly. It is a class diagram of scanner calibration. It is a figure which shows an example of the reading reference value of the chromatic color for a yellow toner correction | amendment, and an achromatic color patch. It is a figure which shows the relationship between the spectral sensitivity of CCD of a blue signal, and the spectral reflectance of yellow toner by the relationship with a wavelength. It is a figure which shows the relationship between the spectral reflectance characteristic of a blue-green ink, the spectral reflectance of the yellow toner of 50% of area ratio, and the read value of a blue signal with a wavelength. It is a figure which shows the quaternary chart of the table for ACC pattern reading value correction | amendment. It is a figure which shows an example of the reading reference value of the chromatic color for a cyan toner correction, and an achromatic color patch. It is a figure which shows the liquid crystal screen which displays an automatic gradation adjustment screen. It is a figure which shows the liquid crystal screen which displays an automatic gradation correction start screen. 3 is a flowchart showing ACC processing by the color copying apparatus of FIG. 2. It is a figure which shows an example of the gradation pattern output on a transfer paper by ACC process. It is a figure which shows the liquid crystal screen which displays the screen which prompts the setting of the transfer paper on the contact glass in FIG. 28 where the gradation pattern was output by the ACC process. It is a figure which shows the liquid crystal screen which displays the reading screen of the transfer sheet by which the gradation pattern was recorded by ACC process. It is a figure which shows the quaternary chart for demonstrating the calculation method in ACC process. It is a figure which shows the example of a production | generation of a Green conversion table. It is a flowchart which shows the gradation conversion table creation process at the time of ACC. It is a flowchart which shows the correction | amendment by scanner data calibration. It is a flowchart which shows the flow of the intermediate result calculation process at the time of initialization of an image processing parameter, or at the time of power activation. It is a flowchart which shows the flow of the intermediate result calculation process at the time of the reading of a reference | standard chart (calibration chart). It is a flowchart which shows the flow of the update process of a scanner vector. It is a flowchart which shows the flow of the update process of a scanner vector inverse matrix. It is a flowchart which shows the flow of the update process of the scanner vector inverse matrix of a predetermined condition. 6 is a flowchart illustrating a flow of printer vector update processing. It is a flowchart which shows the flow of the update process of a scanner (gamma) table. It is a flowchart which shows the flow of the correction process of image data. It is a flowchart which shows the flow of a calculation process of an image processing parameter.

Explanation of symbols

1 Image processing apparatus 300 Image reading means HC reference chart

Claims (10)

The image signal after gradation conversion is converted by the gradation conversion table of the first image signal conversion means for converting the gradation of the input image signal from the image reading means for optically scanning and reading the original image. A color correction unit having a correction unit that corrects the signal color according to a plurality of hue regions formed with a plane provided in the color space parallel to the brightness axis as a boundary;
Reference data storage means for storing reference data corresponding to patches in a reference chart comprising a plurality of achromatic patches of different gradation levels and a plurality of different chromatic patches;
Correction parameter generating means for reading the reference chart by the image reading means, and generating image processing parameters to be set in the color correction means based on the reference data and the read value of the reference chart;
Intermediate result holding means for calculating and holding an intermediate calculation result for obtaining the image processing parameter step by step for each predetermined operation;
Determination information storage means for storing recalculation determination information for determining whether to recalculate the intermediate calculation result;
Based on the recalculation determination information, it is determined whether to recalculate the intermediate calculation result, and when performing recalculation, recalculation means for recalculating the intermediate calculation result;
With
The correction parameter generation means generates the image processing parameter from the intermediate calculation result that has been recalculated or the intermediate calculation result that has not been recalculated .
An image processing apparatus. The intermediate result holding means calculates the intermediate calculation result in a stepwise manner during at least one operation at power-on, initialization, reference chart reading, document reading, and image data processing.
The image processing apparatus according to claim 1. The image processing parameter is set in either the gradation conversion table of the first image signal conversion unit or the correction unit that corrects the image signal.
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. The color correction means is a masking process using linear masking coefficients corresponding to a plurality of hues, and has means for holding an intermediate result of each stage for calculating the linear masking coefficients, and for each hue Determining whether to perform recalculation of the coefficient of the intermediate calculation result;
The image processing apparatus according to claim 3. The reading of the reference chart is prohibited until a predetermined time after the power is turned on,
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. The intermediate calculation result for calculating the linear masking coefficient is provided for each document type, and whether to calculate for each document type can be selected.
The image processing apparatus according to claim 4 or 5, wherein Increase or decrease the intermediate calculation result to be held depending on the amount of volatile memory that can be used.
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. In the case of having a plurality of the image reading means, the intermediate calculation result has for each of the image reading means,
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. By comparing the held intermediate calculation result with the newly corrected intermediate calculation result, it is determined whether to recalculate the intermediate calculation result downstream or the image processing parameter.
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. Means for storing a first correction amount used to determine the image processing parameter;
Means for calculating a difference from the second correction amount obtained by newly reading the reference value chart;
Means for storing a threshold for a difference between the first correction amount and the second correction amount;
Have
Determining whether to recalculate the intermediate calculation result of the image processing parameter based on a result of comparison between a difference between the first correction amount and the second correction amount with a threshold value;
The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus.